As filed with the Securities and Exchange Commission on September 26, 2001

                                                      Registration No. 333-64816
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                      ------------------------------------

                                 POST-EFFECTIVE
                               AMENDMENT NO. 1 TO
                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                           BIOTRANSPLANT INCORPORATED
             (Exact Name of Registrant as Specified in Its Charter)

              DELAWARE                                      04-3119555
     (State or Other Jurisdiction of                     (I.R.S. Employer
     Incorporation or Organization)                      Identification No.)

   CHARLESTOWN NAVY YARD
 BUILDING 75, THIRD AVENUE
CHARLESTOWN, MASSACHUSETTS                                     02129
(Address of Principal Executive Offices)                     (Zip Code)

             ELIGIX, INC. 1997 EQUITY INCENTIVE PLAN, AS AMENDED
                                      AND
       ELIGIX, INC. AMENDED AND RESTATED MANAGEMENT EQUITY INCENTIVE PLAN
                            (Full Title of the Plan)

                              ELLIOT LEBOWITZ, Ph.D.
                            CHIEF EXECUTIVE OFFICER
                           BIOTRANSPLANT INCORPORATED
                              CHARLESTOWN NAVY YARD
                            BUILDING 75, THIRD AVENUE
                        CHARLESTOWN, MASSACHUSETTS 02129
                     (Name and Address of Agent For Service)

                                 (617) 241-5200
          (Telephone Number, Including Area Code, of Agent For Service)





                                Explanatory Note

         The reoffer prospectus set forth below and filed as part of this
Post-Effective Amendment No. 1 to the Registration Statement on Form S-8 has
been prepared in accordance with the requirements of Part I of Form S-3 under
the Securities Act of 1933, as amended, and in accordance with Section C of
the General Instructions to Form S-8. The reoffer prospectus may be used for
reofferings and resales of common stock acquired by the selling stockholders
listed on page 14 of the reoffer prospectus, pursuant to the Eligix, Inc.
Amended and Restated Management Equity Incentive Plan, which was assumed by
BioTransplant on May 15, 2001 in connection with the acquisition of Eligix,
Inc. by BioTransplant. These selling stockholders are affiliates of
BioTransplant Incorporated (as defined in Rule 501(b) of Regulation D of the
Securities Act of 1933).



REOFFER PROSPECTUS

                           BIOTRANSPLANT INCORPORATED

                         451,916 SHARES OF COMMON STOCK

                                ----------------


         This prospectus relates to resales of common stock that we issued to
the selling stockholders listed on page 14. We will not receive any of the
proceeds from the sale of the shares by the selling stockholders.

         The selling stockholders identified in this prospectus, or their
permitted transferees, may offer the shares from time to time through public
or private transactions at prevailing market prices, at prices related to
prevailing market prices or at privately negotiated prices. Each of the
selling stockholders is, as of the date of this prospectus, our affiliate.

         Our common stock is traded on the Nasdaq National Market under the
symbol "BTRN." On September 25, 2001, the last reported sale price of our
common stock on the Nasdaq National Market was $4.50 per share. You are urged
to obtain current market quotations for the common stock.

                                ----------------

         INVESTING IN OUR COMMON STOCK INVOLVES A HIGH DEGREE OF RISK. SEE "RISK
FACTORS" BEGINNING ON PAGE 5.

                                ----------------

         NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS
PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

         Our principal executive offices are located at Building 75, Third
Avenue, Charlestown Navy Yard, Charlestown, Massachusetts 02129 and our
telephone number is (617) 241-5200.

                                ----------------

              The date of this prospectus is September 25, 2001





                        TABLE OF CONTENTS

                                                             PAGE

 Prospectus Summary........................................... 3

 Who We Are................................................... 3

 Risk Factors................................................. 5

 Special Note Regarding Forward-Looking Information...........13

 Use Of Proceeds..............................................14

 Selling Stockholders.........................................14

 Plan Of Distribution.........................................15

 Legal Matters................................................16

 Experts......................................................16

 Where You Can Find More Information..........................16

 Incorporation Of Certain Documents By Reference..............17


         BioTransplant Incorporated's executive offices are located at Building
75, Third Avenue, Charlestown Navy Yard, Charlestown, Massachusetts 02129, and
our telephone number is 617-241-5200. Unless the context otherwise requires,
references in this prospectus to "BioTransplant," "we," "us," and "our" refer to
BioTransplant Incorporated and its subsidiaries.

         BioTransplant(TM), ImmunoCognance(TM), AlloMune(TM), BTI-322(TM) and
Eligix(TM) are our trademarks. This prospectus also contains trademarks and
tradenames of others.

         We have not authorized anyone to provide you with information different
from that contained or incorporated by reference in this prospectus. The selling
stockholders are offering to sell, and seeking offers to buy, shares of our
common stock only in jurisdictions where offers and sales are permitted. The
information contained in this prospectus is accurate only as of the date of this
prospectus, regardless of the time of delivery of this prospectus or of any sale
of common stock.


                                      -2-



                               PROSPECTUS SUMMARY

         THIS SUMMARY HIGHLIGHTS IMPORTANT FEATURES OF THIS OFFERING AND THE
INFORMATION INCLUDED OR INCORPORATED BY REFERENCE IN THIS PROSPECTUS. THIS
SUMMARY DOES NOT CONTAIN ALL OF THE INFORMATION THAT YOU SHOULD CONSIDER BEFORE
INVESTING IN OUR COMMON STOCK. YOU SHOULD READ THE ENTIRE PROSPECTUS CAREFULLY,
ESPECIALLY THE RISKS OF INVESTING IN OUR COMMON STOCK DISCUSSED UNDER "RISK
FACTORS."

                                   WHO WE ARE

         BioTransplant is developing pharmaceutical products and systems to
enable the body's immune system to better tolerate the transplantation of
foreign cells, tissues and organs. Our lead product, the Eligix BCell-HDM
Cell Separation System, received CE Mark approval in February 2001, and is
currently being marketed in Europe. CE mark approval indicates compliance with
European standards for safety and allows certified products to be marketed
and sold in Europe. We began U.S. Phase III clinical trials of this product
in May 2001. In September 2001, we also received CE Mark approval of a second
product, the Eligix TCell-HDM Cell Separation System. The BCell-HDM and
TCell-HDM Cell Separation System products will be commercialized and sold
pursuant to an exclusive distribution agreement with Gambro BCT.

         In addition, MEDI-507, an antibody product, is being developed in
collaboration with MedImmune, Inc. We have exclusively licensed MEDI-507 to
MedImmune as a stand-alone agent, and we are entitled to royalties on product
sales, if any, as well as milestone payments if specific product-related
milestones are achieved. MEDI-507 is currently in multiple Phase II clinical
trials for the treatment of psoriasis.

         We are also independently developing proprietary technology, which
we refer to as ImmunoCognance technology, which is based upon mixing elements
of a donor's immune system with that of a patient in a manner that enables
the patient to recognize the donor's tissues as if those foreign tissues
belonged to the patient. We believe that our ImmunoCognance technology will
have the following benefits when compared to current technologies:

         o        improve clinical outcomes in bone marrow transplantation for
                  cancer and other diseases;

         o        reduce or eliminate the need for long-term administration of
                  potentially debilitating immunosuppressive drugs to a patient
                  after a transplantation procedure;

         o        minimize infection and health complications that may result
                  from conventional therapies used in connection with the
                  transplantation of foreign cells, tissues and organs;

         o        reduce the cost of treating end-stage organ disease; and

         o        increase the supply of cells, tissues and organs available for
                  transplantation procedures.

         Based upon our ImmunoCognance technology, we are developing a portfolio
of products designed to improve therapies associated with organ and bone marrow
transplantation as well as to improve the treatment of cancer, autoimmune
diseases and blood disorders. Our AlloMune System for Cancer is currently in a
multi-center Phase I/II clinical trial for therapy-resistant lymphoma, and we
anticipate filing an investigational new drug application in 2001 for additional
indications. We expect that Phase I clinical studies of our AlloMune System for
Transplantation for human kidney transplantation will begin in 2001.

         On May 15, 2001, we completed our acquisition of Eligix, Inc.
Through this acquisition we gained access to Eligix' patented High Density
Microparticle, or HDM, technology, which is designed to enable the efficient
selection of specific populations of human cells from blood and bone marrow.
Our HDM product candidates, BCell-HDM and TCell-HDM, will target bone marrow
and stem cell transplant procedures. We are targeting these products for the
removal of unwanted or undesirable cells from stem cell transplants and
related blood products to reduce the risk of relapse or graft-versus-host
disease following bone marrow or stem cell transplantation for cancer and
other diseases, including autoimmune and genetic disorders. In August 2001,
we entered into an exclusive distribution agreement with Gambro BCT, a
wholly-owned subsidiary of Gambro AB, for the distribution of our Eligix HDM
cell separation product line. The territory will be worldwide, exclusive of
the U.S., Canada and Japan. Gambro BCT has an option to obtain the exclusive
right to distribute products in the U.S. and Canada, and has a right of first
negotiation with respect to any distribution agreement in Japan. Under the
agreement, we will be responsible for developing, manufacturing and obtaining
CE Mark approval for the HDM cell separation products and Gambro BCT will be
responsible for continued clinical market development and all other aspects
of marketing, sales and distribution.

         In September 2000, we and Novartis Pharma AG formed a new company,
Immerge BioTherapeutics AG, to conduct further research in the area of
xenotransplantation, which is the transplantation of cells, tissues and

                                     -3-




organs from one species to another. Novartis has committed $30 million in
research funding to Immerge over three years, and has exclusively licensed
technology to Immerge in return for a 67% ownership and exclusive development
and marketing rights. BioTransplant has exclusively licensed technology to
Immerge in exchange for a 33% ownership and future royalties from the sale of
any xenotransplantation products by Novartis.

         In addition to our corporate collaboration with MedImmune and our
joint venture with Novartis, we are collaborating with a number of other
organizations, including the Massachusetts General Hospital and the Dana
Farber Cancer Institute, in the fields of cell, tissue and organ
transplantation.

         We believe that we have built a strong patent portfolio relating to
our technology. As of August 31, 2001, we owned or had licensed 37 issued
United States patents and 39 allowed or pending United States patent
applications, as well as applications for foreign patents.

                                     -4-




                                  RISK FACTORS

         AN INVESTMENT IN OUR COMMON STOCK INVOLVES SIGNIFICANT RISKS. YOU
SHOULD CAREFULLY CONSIDER THE FOLLOWING RISKS, TOGETHER WITH ALL OF THE OTHER
INFORMATION INCLUDED IN THIS PROSPECTUS OR INCORPORATED HEREIN BY REFERENCE,
BEFORE YOU DECIDE TO BUY OUR COMMON STOCK. IF ANY OF THE FOLLOWING RISKS
ACTUALLY OCCURS, OUR BUSINESS, FINANCIAL CONDITION OR RESULTS OF OPERATIONS
COULD BE HARMED. IN SUCH AN EVENT, THE TRADING PRICE OF OUR COMMON STOCK COULD
DECLINE AND YOU MAY LOSE ALL OR PART OF YOUR INVESTMENT.

              RISKS RELATED TO OUR BUSINESS, INDUSTRY AND STRATEGY

         THERE ARE UNCERTAINTIES AS TO THE EFFECTIVENESS OF OUR TECHNOLOGICAL
APPROACHES AND, AS A RESULT, WE MAY NOT BE ABLE TO SUCCESSFULLY DEVELOP AND
COMMERCIALIZE ANY PRODUCTS.

         Our future success depends on the successful development of our
ImmunoCognance and Eligix Cell Separation System technologies. The MEDI-507
antibody product under development, the prototype AlloMune System and the Eligix
Cell Separation System have been tested in relatively few patients and we may
not be able to demonstrate the clinical benefits of these products in a larger
patient population. Furthermore, the technology that we have exclusively
licensed to our joint venture with Novartis Pharma AG is based upon the
transplantation of organs from swine into humans. To our knowledge,
transplantation of swine organs has never been tested in humans. As a
consequence, we are not sure whether any of our or our collaborators' potential
products will be effective in treating any of the disorders we have targeted. In
addition, these products may prove to have undesirable or unintended side
effects, toxicities or other characteristics that may prevent or limit their
commercial use. If our technological approach is not successful or accepted,
then neither we nor our collaborators will be able to develop or commercialize
these products.

         WE ARE DEPENDENT ON MEDIMMUNE AND NOVARTIS TO DEVELOP, MANUFACTURE AND
SELL TECHNOLOGIES EXCLUSIVELY LICENSED BY US, AND IF THESE PARTIES ARE NOT
SUCCESSFUL, THEN WE WILL NOT ACHIEVE SIGNIFICANT REVENUES BASED ON THESE
TECHNOLOGIES.

         We have a collaborative agreement with MedImmune under which we have
provided MedImmune with the exclusive worldwide right to develop and
commercialize products derived from the BTI-322 and MEDI-507 antibodies. In
addition, our joint venture with Novartis, Immerge BioTherapeutics, has
exclusively licensed to Novartis the right to develop and commercialize any
products derived from Immerge's research program in xenotransplantation,
which refers to the transplantation of cells, tissues and organs from one
species to another. Under each of these collaborative agreements, we have the
right to receive royalties on product sales, if any. Our ability to achieve
royalty revenue under these arrangements will be heavily dependent on the
efforts and activities of MedImmune and Novartis. Our arrangements with
MedImmune and, through our joint venture, with Novartis allow them
significant discretion in determining the efforts and resources that they
will apply to the development and commercialization of products based upon
our technologies. Accordingly, we are unable to control whether or not
products based upon our technologies will be scientifically or commercially
successful.

         The risks that we face in connection with our agreements with MedImmune
and Novartis include the following:

         o        These agreements are subject to termination on short notice.
                  Specifically, MedImmune may terminate the agreement with us,
                  and Novartis has the right to terminate the agreement with the
                  joint venture, on 60 days' notice as a result of an uncured
                  material breach by us or the joint venture, as the case may
                  be. If either MedImmune or Novartis terminates its
                  collaboration with us, or the joint venture, in the case of
                  Novartis, it may be difficult for us to attract a new partner
                  to develop and commercialize products based on our
                  technologies and may adversely affect the perception of us in
                  the business and financial communities.

         o        If MedImmune or Novartis were to breach or terminate its
                  agreement with us, or the joint venture, in the case of
                  Novartis, reduce its funding or otherwise fail to conduct the
                  collaboration

                                     -5-




                  successfully, we could be required to devote additional
                  internal resources to the program that is the subject of the
                  collaboration, scale back or terminate the program or seek an
                  alternative partner.

         o        MedImmune and Novartis may pursue higher priority programs or
                  change the focus of their research and development programs,
                  which could affect either party's commitment to us.

         o        If any product under development is approved for marketing,
                  any reductions in marketing or sales efforts or a
                  discontinuation of marketing or sales of that product by
                  MedImmune or Novartis would reduce any revenues we may then
                  be receiving on sales of the product.

         WE WILL DEPEND ON OUR ELIGIX CELL SEPARATION SYSTEM PRODUCTS FOR
SUBSTANTIALLY ALL OF OUR NEAR-TERM REVENUE, AND IF THE CELL SEPARATION SYSTEM
PRODUCTS DO NOT GAIN WIDESPREAD MARKET ACCEPTANCE, THEN OUR REVENUE WILL NOT
GROW.

         We only recently received CE mark approval to sell our lead
products, the BCell-HDM and TCell-HDM Cell Separation Systems, in the
European Union. To date, we have sold only relatively few BCell-HDM devices.
Because we currently depend on European sales of our Cell Separation System
products to generate all of our near-term revenue, if we, or our distribution
partner, Gambro, fail to achieve widespread market acceptance of the products
in Europe we will not be able to grow our product revenue.

         WE WILL NOT BE PROFITABLE IF THE MARKET IS NOT RECEPTIVE TO NEW
PRODUCTS UPON THEIR INTRODUCTION.

         The commercial success of our products when and if they are approved
for marketing will depend upon their acceptance by the medical community and
third-party payors as clinically useful, cost effective and safe. All of the
products that we are developing and/or commercializing are based upon new
technologies or therapeutic approaches. As a result, it may be more difficult
for us to convince the medical community and third-party payors to accept and
use any products we may develop.

         Other factors that we believe will materially affect market acceptance
of our products under development include:

         o        the timing of our receipt of marketing approvals, if any,
                  and the countries in which approvals are obtained;

         o        the safety, efficacy and ease of administration of any
                  products we develop;

         o        the success of our physician education programs; and

         o        the availability of government and third-party payor
                  reimbursement of any products we develop.

         XENOTRANSPLANTATION INVOLVES RISKS WHICH HAVE RESULTED IN ADDITIONAL
FDA OVERSIGHT AND WHICH IN THE FUTURE MAY RESULT IN ADDITIONAL REGULATION.

         Xenotransplantation poses a risk that viruses or other animal
pathogens may be unintentionally transmitted to a human patient. The United
States Food and Drug Administration, or FDA, will require testing to
determine whether infectious agents, including specific viruses referred to
as porcine endogenous retroviruses, also known as PERV, are present in
patients who have received cells, tissues or organs from miniature swine.
While porcine endogenous retroviruses have not been shown to cause any
disease in pigs, it is not known what effect, if any, these retroviruses may
have on humans.

         Other companies are currently conducting clinical trials involving the
transplantation of pig cells into humans. The FDA requires lifelong monitoring
of these transplant recipients. If porcine endogenous retroviruses or any other
virus or infectious agent is detected in tests or samples from these transplant
recipients, the FDA may require Novartis to halt its clinical trials and perform
additional tests to assess the risk of infection to potential patients. This
could result in delays in the successful development and commercialization of
any xenotransplantation products.

                                     -6-




         The FDA has proposed, but not yet established, definitive regulatory
guidelines for xenotransplantation. We and Novartis may not be able to comply
with any final guidelines the FDA may issue.

         RISKS RELATING TO OUR FINANCIAL RESULTS AND NEED FOR FINANCING

         WE WILL REQUIRE SUBSTANTIAL ADDITIONAL FINANCING IN THE NEAR TERM,
WHICH MAY BE DIFFICULT TO OBTAIN AND MAY DILUTE YOUR OWNERSHIP INTEREST IN US.

         We anticipate that our existing funds will be sufficient to fund our
operating and capital requirements through the second quarter of 2002. We
expect to use rather than generate funds from operations for the foreseeable
future. In particular, we will require substantial funds to conduct research
and development, including preclinical testing and clinical trials of our
AlloMune System and Eligix Cell Separation System and to manufacture and
market products that are approved for commercial sale. If we cannot raise
more funds, we could be required to reduce our capital expenditures, scale
back our research and product developments, reduce our workforce and license
to others products or technologies we would otherwise seek to commercialize
ourselves.

         We may seek additional funding through collaborative arrangements,
borrowing money and by the sale of additional equity securities. Any sales of
additional equity securities are likely to result in further dilution to our
then existing stockholders. Further, if we issue additional equity securities,
the new equity securities may have rights, preferences or privileges senior to
those of existing holders of our common stock. We may also borrow money from
conventional lenders, possibly at high interest rates, which will increase the
risk of your holdings. Despite our efforts, additional funding may not be
available to us at all or only on terms that are unacceptable to us. We also
could be required to seek funds through arrangements with collaborative partners
or others that may require us to relinquish rights to our technologies, product
candidates or products which we would otherwise pursue on our own.

         Even if we are able to raise additional funds in a timely manner, our
future capital requirements will vary depending on many factors, including the
following:

         o        continued progress in our research and development programs,
                  as well as the magnitude of these programs;

         o        the resources required to successfully complete our clinical
                  trials;

         o        the time and costs involved in obtaining regulatory approvals;

         o        the cost of manufacturing and commercialization activities;

         o        the cost of any additional facilities requirements;

         o        the timing, receipt and amount of milestone and other payments
                  from collaborative partners;

         o        the timing, receipt and amount of sales and royalties from our
                  potential products in the market; and

         o        the costs involved in preparing, filing, prosecuting,
                  maintaining and enforcing patent claims and other
                  patent-related costs, including litigation costs and the costs
                  of obtaining any required licenses to technologies.

         WE HAVE INCURRED SUBSTANTIAL LOSSES, EXPECT TO CONTINUE TO INCUR
ADDITIONAL LOSSES AND WILL NOT BE SUCCESSFUL UNTIL WE REVERSE THIS TREND.

         We have incurred losses in each year since our date of organization. We
expect to incur operating losses for the foreseeable future.

                                     -7-




         To date, we have not successfully commercialized and sold the types of
products we are currently developing. Many of the products that we are
developing will require additional research and development, extensive
preclinical studies and clinical trials and regulatory approval before they can
be sold commercially in major markets such as the United States. In particular,
we may need to successfully develop several new technologies in order to
complete development of our AlloMune System. If we do not successfully develop
and commercialize any products, we will never become profitable.

         To date, we have generated substantially all of our revenues from
payments from our collaborative partners. In 2000, we generated approximately
$4.6 million, or 100% of our total revenue, from our collaboration with
Novartis, which was terminated in October 2000 in connection with the formation
of our joint venture with Novartis. We have not received significant revenues
from the sale of products. We anticipate that it may be a number of years, if
ever, before we will receive significant revenues from product sales or
royalties.

                RISKS RELATING TO CLINICAL AND REGULATORY MATTERS

         IF OUR CLINICAL TRIALS ARE NOT SUCCESSFUL OR ARE NOT COMPLETED ON A
TIMELY BASIS, WE WILL NOT BE ABLE TO DEVELOP AND COMMERCIALIZE ANY RELATED
PRODUCTS AND, THEREFORE, WE WILL NOT ACHIEVE PROFITABILITY.

         To obtain regulatory approvals for the commercial sale of our products,
we and our collaborative partners will need to complete extensive clinical
trials in humans to demonstrate the safety and efficacy of the products. We have
had limited experience in conducting clinical trials.

         Prior to commencing new clinical trials, we must submit investigational
new drug and/or investigational device exemption applications to the FDA. Even
if we receive authorization from the FDA to commence clinical trials, we or our
collaborative partners may not be able to successfully complete these trials
within an acceptable timeframe, if at all. How quickly we and our collaborative
partners complete clinical trials is dependent in part upon the rate of
enrollment of patients. Patient enrollment is a function of many factors,
including the size of the patient population, the proximity of patients to
clinical sites, the eligibility criteria for the study and the existence of
competitive clinical trials. In particular, the patient population for a number
of our potential products is small. If we experience delays in patient
enrollment, we may incur additional costs and delay our research and development
programs.

         Furthermore, we, our collaborative partners or the FDA may suspend our
clinical trials at any time on various grounds, including a finding that the
patients in the trials are being exposed to unacceptable health risks. Finally,
our clinical trials, if completed, may not show the potential product to be safe
or effective, thereby preventing regulatory approval.

         WE ARE DEPENDENT ON OUR COLLABORATIVE PARTNERS TO CONDUCT CLINICAL
TRIALS ON OUR MEDI-507 AND XENOTRANSPLANTATION PRODUCTS AND, THEREFORE, WE ARE
NOT IN CONTROL OF THE TIMING OF THESE CLINICAL TRIALS.

         We are dependent upon MedImmune to conduct clinical trials with respect
to MEDI-507 and will be dependent upon Novartis to conduct clinical trials for
the development of xenotransplantation products, if any, that arise out of our
joint venture's research program. We may become dependent upon other third
parties to conduct future clinical trials of our AlloMune System and Eligix Cell
Separation System. As a result, we will have less control over these clinical
trials than if we were conducting the trials directly. Consequently, these
trials may not begin or be completed on a schedule that is acceptable to us.

         THE APPROVAL PROCESS IS COSTLY AND LENGTHY AND WE MAY NOT OBTAIN AND
MAINTAIN THE REGULATORY APPROVALS REQUIRED TO SUCCESSFULLY MARKET AND SELL OUR
PRODUCTS.

         We must obtain regulatory approval for our ongoing development
activities and before marketing or selling any of our products. We may not
receive regulatory approvals to conduct clinical trials of our products or to
manufacture or market our products. In addition, regulatory agencies may not
grant such approvals on a timely basis or may revoke previously granted
approvals or impose fines, suspensions, product recalls and other sanctions if
we fail to comply with applicable regulatory requirements.

                                     -8-




         The process of obtaining FDA and other required regulatory approvals is
expensive and typically takes a number of years, depending on the complexity and
novelty of the product. Any delay in obtaining or failure to obtain required
clearance or approval of a product by the appropriate regulatory authorities,
would materially adversely affect our ability to generate revenues from the
affected product. We have limited experience in filing and prosecuting the
applications required to gain regulatory approval.

         There is limited regulatory precedent for the approval of products
based upon the technologies that we are employing to develop products. The
AlloMune System and Eligix Cell Separation System are based on new
technologies and/or new therapeutic approaches that have not been extensively
tested in humans. Accordingly, the regulatory requirements governing these
products under development may be more rigorous than for conventional
products. In addition, the FDA has not yet established final or comprehensive
guidelines for xenotransplantation. As a result, we may experience a longer
regulatory process in connection with any products that we or our
collaborators seek to develop based on these new technologies and/or new
therapeutic approaches.

         We also are subject to numerous foreign regulatory requirements
governing the design and conduct of the clinical trials and the manufacturing
and marketing of our future products. The approval procedure varies among
countries. The time required to obtain foreign approvals often differs from
that required to obtain FDA approvals. Moreover, even if we receive FDA
approval, we may not receive necessary approvals by regulatory authorities in
other countries.

         All of these regulatory risks also are applicable to development,
manufacturing and marketing undertaken by our key collaborators, MedImmune and
Novartis, and any other future collaborators who may seek to develop, market and
sell products based upon our technologies.

                     RISKS RELATING TO INTELLECTUAL PROPERTY

         WE MAY NOT BE ABLE TO OBTAIN PATENT PROTECTION FOR OUR DISCOVERIES AND
WE MAY INFRINGE PATENT RIGHTS OF THIRD PARTIES.

         Our success depends in significant part on our ability to:

         o        obtain patents;

         o        protect trade secrets;

         o        operate without infringing upon the proprietary rights of
                  others; and

         o        prevent others from infringing on our proprietary rights.

         The validity and permissible scope of claims covered in patents
relating to our technology involve important unresolved legal principles.
Furthermore, there is substantial uncertainty as to whether human clinical data
will be required for issuance of patents for human therapeutics. If human
clinical data are required, our ability to obtain patent protection could be
delayed or otherwise adversely affected.

         Patents may not issue from any patent applications that we own or
license. If patents do issue, the claims allowed may not be sufficiently broad
to protect our technology. In addition, issued patents that we own or license
may be challenged, invalidated or circumvented. Our patents also may not afford
us protection against competitors with similar technology. Because patent
applications in the United States are maintained in secrecy until patents issue,
third parties may have filed or maintained patent applications for technology
used by us or covered by our pending patent applications without our being aware
of these applications.

         We may not hold proprietary rights to all of the patents related to our
proposed products or services. These patents may be owned or controlled by third
parties. As a result, we or our collaborative partners may be required to obtain
licenses under third-party patents to market our proposed products or services.
If licenses are not available on acceptable terms, we or our collaborative
partners will not be able to market these products or services.

                                     -9-




         IF WE LOSE IMPORTANT LICENSE RIGHTS, WE MAY BE UNABLE TO SUCCESSFULLY
DEVELOP AND COMMERCIALIZE OUR PRODUCTS AND ACHIEVE PROFITABILITY.

         We are a party to technology in-licenses with the Catholic University
of Louvain, the Alberta Research Council and the Coulter Corporation. We expect
to enter into additional licenses in the future. These in-licenses relate to
important technologies that may be necessary for the development and
commercialization of our products. These licenses impose various
commercialization, indemnification, royalty, insurance and other obligations on
us. Although we currently meet the requirements imposed by the licenses, if we
fail to comply with these requirements in the future, the licensors will have
the right to terminate these licenses or make the licenses non-exclusive, which
could affect our ability to exploit important technologies that are required for
successful development of our products.

          RISKS RELATING TO PRODUCT MANUFACTURING, MARKETING AND SALES

         WE HAVE ONLY LIMITED SALES AND MARKETING EXPERIENCE AND WILL DEPEND
SIGNIFICANTLY ON THIRD PARTIES WHO MAY NOT SUCCESSFULLY COMMERCIALIZE OUR
PRODUCTS.

         We have only limited sales, marketing and distribution experience.
We plan to rely significantly on sales, marketing and distribution
arrangements with third parties, including our collaborative partners. For
example, we have granted Gambro BCT exclusive rights to market our HDM cell
separation product line worldwide, except in the U.S., Canada and Japan.
Gambro also has an option to gain exclusive rights in the U.S. and Canada and
a right of first negotiation with respect to any distribution agreement in
Japan. We have also granted MedImmune exclusive marketing rights to the
MEDI-507 product under development and have granted Novartis exclusive
worldwide rights to develop and market products based upon our
xenotransplantation technologies. We may have to enter into additional
marketing arrangements in the future and we may not be able to enter into
these additional arrangements on terms which are favorable to us, if at all.
In addition, we may have limited or no control over the sales, marketing and
distribution activities of these third parties and sales through these third
parties could be less profitable to us than direct sales. These third parties
could sell competing products and may devote insufficient sales efforts to
our products. Our future revenues will be materially dependent upon the
success of the efforts of these third parties. Our ability to terminate these
agreements unilaterally is limited in certain cases. If these third parties
do not successfully commercialize our current and any future products that
they may have the right to commercialize, we may never generate significant
revenue or achieve profitability.

         We may seek to independently market products that are not already
subject to marketing agreements with other parties. If we determine to perform
sales, marketing and distribution functions ourselves, we could face a number of
additional risks, including:

         o        we may not be able to attract and build a significant
                  marketing staff or sales force;

         o        the cost of establishing a marketing staff or sales force may
                  not be justifiable in light of the revenues generated by any
                  particular product; and

         o        our direct sales and marketing efforts may not be successful.

         IF WE EXPERIENCE MANUFACTURING DELAYS OR INTERRUPTIONS IN PRODUCTION OF
OUR ELIGIX CELL SEPARATION SYSTEM, THEN WE MAY EXPERIENCE CUSTOMER
DISSATISFACTION AND OUR REPUTATION COULD SUFFER.

         If we fail to produce enough products at our own manufacturing facility
or at a third-party manufacturing facility, we may be unable to deliver products
to our customers on a timely basis, which could lead to customer dissatisfaction
and could harm our reputation and ability to compete. We currently produce key
components of our Eligix Cell Separation System in one manufacturing facility.
We would likely experience significant delays or cessation in producing our
Eligix Cell Separation System at this facility if a labor strike, natural
disaster, or other supply disruption were to occur. If we are unable to
manufacture our Eligix Cell Separation System at our own facility, we may be
required to enter into arrangements with one or more contract manufacturing
companies. We could encounter delays or difficulties establishing relationships
with contract manufacturers or in establishing agreements on terms that are
favorable to us. In addition, if we are required to depend on third-party
manufacturers, our profit margins may be lower, which will make it more
difficult for us to achieve profitability.

                                    -10-




         WE WILL DEPEND ON THIRD-PARTY MANUFACTURERS TO PRODUCE SOME OF OUR
PRODUCTS UNDER DEVELOPMENT, AND IF THESE THIRD PARTIES DO NOT SUCCESSFULLY
MANUFACTURE OUR PRODUCTS OUR BUSINESS WILL BE HARMED.

         We currently rely upon MedImmune to produce material for preclinical
and clinical testing of MEDI-507 and expect to continue to do so in the future.
In addition, if we receive the necessary regulatory approvals for other products
under development, we also expect to rely upon third parties, including our
collaborative partners, to produce materials required for commercial production.
To the extent that we enter into manufacturing arrangements with third parties,
we will be dependent upon these third parties to perform their obligations in a
timely manner. If third-party manufacturers with whom we contract fail to
perform their obligations, we may be adversely affected in a number of ways,
including:

         o        we may not be able to initiate or continue clinical trials of
                  products that are under development;

         o        we may be delayed in submitting applications for regulatory
                  approvals for our products; and

         o        ultimately, we may not be able to meet commercial demands for
                  our products.

         IF WE OR OUR THIRD-PARTY MANUFACTURERS FAIL TO COMPLY WITH REGULATORY
REQUIREMENTS, WE COULD EXPERIENCE DISRUPTIONS IN THE MANUFACTURE AND SALE OF OUR
PRODUCTS.

         Manufacturers, including us, must adhere to the FDA's current good
manufacturing practices regulations, which are enforced by the FDA through
its facilities inspection program. We and any third party manufacturers may
not be able to comply or maintain compliance with good manufacturing
practices regulations. If we or our manufacturers fail to comply, our receipt
of premarket approval could be significantly delayed, or we or the third
party manufacturer could be subject to FDA enforcement action, including an
embargo on imported devices. For a premarket approval device, if we change
our manufacturing facility or switch to a third-party manufacturer we will be
required to submit a premarket approval application supplement before the
change is implemented.

         BECAUSE WE RELY ON A LIMITED NUMBER OF SUPPLIERS, WE MAY EXPERIENCE
DIFFICULTY IN MEETING OUR CUSTOMERS' DEMANDS FOR OUR ELIGIX CELL SEPARATION
SYSTEM PRODUCT IN A TIMELY MANNER OR WITHIN BUDGET.

         We currently purchase key components of our Eligix Cell Separation
System from a variety of outside sources. Some of these components may only be
available to us through a few sources. We generally do not have long-term
agreements with any of our suppliers.

         Our reliance on our suppliers exposes us to risks, including:

         o        the possibility that one or more of our suppliers could
                  terminate their services at any time without penalty;

         o        the potential inability of our suppliers to obtain required
                  components;

         o        the potential delays and expenses of seeking alternative
                  sources of supply;

         o        reduced control over pricing, quality and timely delivery due
                  to the difficulties in switching to alternative suppliers; and

         o        the possibility that one or more of our suppliers could fail
                  to satisfy any of the FDA's required current good standing
                  manufacturing practices regulations.

         Consequently, in the event that our suppliers delay or interrupt the
supply of components for any reason, our ability to produce and supply our
products could be impaired, which could lead to customer dissatisfaction.

                                    -11-




                    RISK RELATING TO OUR FOREIGN OPERATIONS

         IF WE ARE UNABLE TO MEET THE OPERATIONAL, LEGAL AND FINANCIAL
CHALLENGES THAT WE WILL ENCOUNTER IN OUR INTERNATIONAL OPERATIONS, WE MAY NOT BE
ABLE TO GROW OUR BUSINESS.

         We currently expect to derive our near-term revenue from the sale by
a distributor of our Eligix Cell Separation Device in the European Union. We
are subject to a number of challenges which specifically relate to our
international business activities. Our international operations may not be
successful if we are unable to meet and overcome these challenges, which
would limit the growth of our business. These challenges include:

         o        failure of local laws to provide the same degree of protection
                  against infringement of our intellectual property;

         o        protectionist laws and business practices that favor local
                  competitors, which could slow our growth in international
                  markets;

         o        potentially longer sales cycles to sell products, which could
                  slow our revenue growth from international sales; and

         o        potentially longer accounts receivable payment cycles and
                  difficulties in collecting accounts receivable.

                    RISK RELATING TO THE ELIGIX ACQUISITION

         WE FACE CHALLENGES IN INTEGRATING ELIGIX INTO BIOTRANSPLANT AND, AS
A RESULT, MAY NOT REALIZE THE EXPECTED BENEFITS OF THE MERGER.

         In May 2001, we acquired Eligix through a merger. The merger
involves the integration of two different companies that have previously
operated independently. Integrating Eligix' operations, technologies and
personnel with those of BioTransplant is a complex process. We may not be
able to complete the integration rapidly. After the integration, the combined
company may not achieve the expected benefits of the merger. The diversion of
the attention of our management and any difficulties encountered in the
process of combining our companies could lead to unanticipated liabilities
and costs and cause the disruption of, or a loss of momentum in, the business
activities of the combined company. Further, the process of combining our
companies could negatively affect employee morale and the ability of the
combined company to retain some of its key employees after the merger. As a
consequence, we may not successfully integrate Eligix or profitably manage
the combined company and may incur severance-related costs. In addition, the
combined company may not achieve revenues, net income or loss levels,
efficiencies or synergies that justify the merger, and the merger may not
result in earnings for the combined company in any future period.

                                    -12-




                       RISKS RELATING TO OUR COMMON STOCK

         OUR STOCK PRICE IS HIGHLY VOLATILE, WHICH COULD CAUSE YOU TO LOSE
ALL OR PART OF YOUR INVESTMENT.

         The market price of our common stock is highly volatile. For example,
during the past three years, our stock price fluctuated from a low sale price of
$1.00 in the quarter ended December 31, 1998 to a high sale price of $23.00 in
the quarter ended March 31, 2000. Prices for our common stock will be determined
in the market place and may be influenced by many factors, including variations
in our financial results and investors' perceptions of us, as well as their
perceptions of general economic, industry and market conditions. Broad market
fluctuations may adversely affect the market price of our common stock and may
cause a rapid and substantial decline in the value of your investment in our
common stock.

               SPECIAL NOTE REGARDING FORWARD-LOOKING INFORMATION

         We include and incorporate in this prospectus forward-looking
statements within the meaning of Section 27A of the Securities Act of 1933 and
Section 21E of the Securities Exchange Act of 1934. All statements, other than
statements of historical facts, that we include or incorporate in this
prospectus, including regarding our strategy, future operations, financial
position, future revenues, projected costs, prospects, plans and objectives of
management, are forward-looking statements. We use the words "anticipates,"
"believes," "estimates," "expects," "intends," "may," "plans," "projects,"
"will," "would" and similar expressions to identify forward-looking statements,
although not all forward-looking statements contain these identifying words. We
cannot guarantee that we actually will achieve the plans, intentions or
expectations disclosed in our forward-looking statements and you should not
place undue reliance on our forward-looking statements. Actual results or events
could differ materially from the plans, intentions and expectations we disclose
in the forward-looking statements we make. We have included important factors in
the cautionary statements included or incorporated in this prospectus,
particularly under the heading "Risk Factors", that we believe could cause
actual results or events to differ materially from the forward-looking
statements that we make. Our forward-looking statements do not reflect the
potential impact of future events, including any future acquisitions, mergers,
dispositions, joint ventures or investments we may make. We caution you that we
may not update any or all of the forward-looking statements we make in this
prospectus and incorporate in this prospectus by reference to other documents.

                                    -13-




                                 USE OF PROCEEDS

         We will not receive any proceeds from the sale of shares by the selling
stockholders.

         The selling stockholders will pay any underwriting discounts and
commissions and expenses incurred by the selling stockholders for brokerage,
accounting, tax or legal services or any other expenses incurred by the selling
stockholders in disposing of the shares. We will bear all other costs, fees and
expenses incurred in effecting the registration of the shares covered by this
prospectus, including, without limitation, all registration and filing fees,
Nasdaq listing fees and fees and expenses of our counsel and our accountants.

                              SELLING STOCKHOLDERS

         This prospectus relates to possible sales by the selling
stockholders, each of whom is an affiliate of BioTransplant (as defined in
Rule 501(b) of Regulation D of the Securities Act of 1933). The selling
stockholders are offering up to a total of 451,916 shares of common stock. We
issued the shares of common stock offered herein and covered by this
prospectus to the selling stockholders pursuant to the Eligix, Inc. Amended
and Restated Management Equity Incentive Plan, which we assumed in connection
with our acquisition of Eligix. The following table sets forth, to our
knowledge, certain information about the selling stockholders.

         Beneficial ownership is determined in accordance with the rules of
the SEC, and includes voting or investment power with respect to shares.
Unless otherwise indicated below, to our knowledge, all persons named in the
table have sole voting and investment power with respect to their shares of
common stock, except to the extent authority is shared by spouses under
applicable law. The table below includes shares subject to options which will
be exercisable within 60 days following September 10, 2001. The inclusion of
any shares in this table does not constitute an admission of beneficial
ownership for the person named below.

         We do not know when or in what amounts a selling stockholder may offer
shares for sale. The selling stockholders may not sell any or all of the shares
offered by this prospectus. Because the selling stockholders may offer all or
some of the shares pursuant to this offering, and because there are currently no
agreements, arrangements or understandings with respect to the sale of any of
the shares, we cannot estimate the number of the shares that will be held by the
selling stockholders after completion of the offering. However, for purposes of
this table, we have assumed that, after completion of the offering, none of the
shares covered by this prospectus will be held by the selling stockholders.

         To our knowledge, except as noted in this paragraph and in the table
below, none of the selling stockholders has held any position or office with,
or has otherwise had a material relationship with, us or any of our
subsidiaries within the past three years. In May 2001, BioTransplant acquired
Eligix pursuant to an agreement and plan of merger by and among
BioTransplant, BT/EL Acquisition Co., a wholly-owned subsidiary of
BioTransplant, and Eligix. Pursuant to the agreement and plan of merger,
BT/EL Acquisition Co. merged with and into Eligix, whereupon Eligix became a
wholly-owned subsidiary of BioTransplant. Walter C. Ogier was President,
Chief Executive Officer and a director of Eligix from November 1997 to May
2001. James Embree was Vice President, Manufacturing of Eligix from January
1998 to May 2001. Tara Clark was Vice President, Marketing of Eligix from
September 1999 to May 2001. Judith Sommer was Vice President, Quality
Assurance of Eligix from September 1998 until May 2001. Constance Garrison
was Director of Regulatory Affairs of Eligix from April 1997 to May 2001.



                                                            Shares of Common Stock                       Shares of Common Stock to
                                                           Beneficially Owned Prior       Number of        be Beneficially Owned
                                  Relationship                   to Offering               Shares of           After Offering
                                     With                 -------------------------     Common Stock     -------------------------
   Name of Selling Stockholder    BioTransplant            Number        Percentage     Being Offered       Number      Percentage
   ---------------------------    -------------           --------       ----------     -------------    -----------    ----------
                                                                                                          
Walter C. Ogier                   President               278,177(1)       1.3%           165,617         112,560(1)        *
James Embree                      Senior Vice President   129,765(2)        *              89,870          39,895(2)        *
Judith Sommer                     Vice President          112,105(3)        *              75,952          36,153(3)        *
Tara Clark                        Vice President          107,962(4)        *              84,051          23,911(4)        *
Constance Garrison                Vice President           51,410(5)        *              36,426          14,984(5)        *


--------------------------
*   Less than one percent.

(1) Includes 112,560 shares of common stock which Mr. Ogier has the right to
    acquire within 60 days of September 10, 2001 upon the exercise of stock
    options.

(2) Includes 39,895 shares of common stock which Mr. Embree has the right to
    acquire within 60 days of September 10, 2001 upon the exercise of stock
    options.

(3) Includes  36,153 shares of common stock which Ms. Sommer has the right to
    acquire within 60 days of September 10, 2001 upon the exercise of stock
    options.

(4) Includes 23,911 shares of common stock which Ms. Clark has the right to
    acquire within 60 days of September 10, 2001 upon the exercise of stock
    options.

(5) Includes 9,984 shares of common stock which Ms. Garrison has the right to
    acquire within 60 days of September 10, 2001 upon the exercise of stock
    options.

                                    -14-




                              PLAN OF DISTRIBUTION

         The shares covered by this prospectus may be offered and sold from
time to time by the selling stockholders. This prospectus also covers sales
by permitted transferees of the selling stockholders. A permitted transferee
is a family member who has acquired the shares of common stock from a selling
stockholder through a gift or domestic relations order and without paying
value for the shares. A family member includes any child, stepchild,
grandchild, parent, stepparent, grandparent, spouse, former spouse, sibling,
niece, nephew, mother-in-law, father-in-law, son-in-law, daughter-in-law,
brother-in-law, or sister-in-law, including adoptive relationships, any
person sharing the employee's household (other than a tenant or employee), a
trust in which these persons have more than fifty percent of the beneficial
interest, a foundation in which these persons (or a selling stockholder)
control the management of assets, and any other entity in which these persons
(or a selling stockholder) own more than fifty percent of the voting
interests. The term "selling stockholder" hereafter includes permitted
transferees.

         The selling stockholders will act independently of us in making
decisions with respect to the timing, manner and size of each sale. Such
sales may be made on one or more exchanges or in the over-the-counter market
or otherwise, at prices and under terms then prevailing or at prices related
to the then current market price or in negotiated transactions. The selling
stockholders may sell their shares by one or more of, or a combination of,
the following methods:

         o        purchases by a broker-dealer as principal and resale by such
                  broker-dealer for its own account pursuant to this prospectus;

         o        ordinary brokerage transactions and transactions in which the
                  broker solicits purchasers;

         o        block trades in which the broker-dealer so engaged will
                  attempt to sell the shares as agent but may position and
                  resell a portion of the block as principal to facilitate the
                  transaction;

         o        an over-the-counter distribution in accordance with the rules
                  of the Nasdaq National Market;

         o        in privately negotiated transactions; and

         o        in options transactions.

         In addition, any shares that qualify for sale pursuant to Rule 144
of the Securities Act may be sold under Rule 144 rather than pursuant to this
prospectus.

         To the extent required, this prospectus may be amended or
supplemented from time to time to describe a specific plan of distribution.
In connection with distributions of the shares or otherwise, the selling
stockholders may enter into hedging transactions with broker-dealers or other
financial institutions. The selling stockholders may also enter into option
or other transactions with broker-dealers or other financial institutions
which require the delivery to such broker-dealer or other financial
institution of shares offered by this prospectus, which shares such
broker-dealer or other financial institution may resell pursuant to this
prospectus (as supplemented or amended to reflect such transaction). The
selling stockholders may also pledge shares to a broker-dealer or other
financial institution, and, upon a default, such broker-dealer or other
financial institution may effect sales of the pledged shares pursuant to
this prospectus (as supplemented or amended to reflect such transaction).

         In effecting sales, broker-dealers or agents engaged by the selling
stockholders may arrange for other broker-dealers to participate. Broker-dealers
or agents may receive commissions, discounts or concessions from the selling
stockholders in amounts to be negotiated immediately prior to the sale.

         In offering the shares covered by this prospectus, the selling
stockholders and any broker-dealers who execute sales for the selling
stockholders may be deemed to be "underwriters" within the meaning of the
Securities Act in connection with such sales. Any profits realized by the
selling stockholders and the compensation of any broker-dealer may be deemed to
be underwriting discounts and commissions.

         In order to comply with the securities laws of certain states, if
applicable, the shares must be sold in such jurisdictions only through
registered or licensed brokers or dealers. In addition, in certain states the
shares may not be sold unless they have been registered or qualified for sale in
the applicable state or an exemption from the registration or qualification
requirement is available and is complied with.

                                    -15-




         We have advised the selling stockholders that the anti-manipulation
rules of Regulation M under the Exchange Act may apply to sales of shares in
the market and to the activities of the selling stockholders. In addition, we
will make copies of this prospectus available to the selling stockholders for
the purpose of satisfying the prospectus delivery requirements of the
Securities Act. The selling stockholders may indemnify any broker-dealer that
participates in transactions involving the sale of the shares against certain
liabilities, including liabilities arising under the Securities Act.

         At the time a particular offer of shares is made, if required, a
prospectus supplement will be distributed that will set forth:

         o        the number of shares being offered;

         o        the terms of the offering, including the name of any
                  underwriter, dealer or agent;

         o        the purchase price paid by any underwriter;

         o        any discount, commission and other item constituting
                  compensation;

         o        any discount, commission or concession allowed or reallowed
                  or paid to any dealer; and

         o        the proposed selling price to the public.

                                  LEGAL MATTERS

         The validity of the shares offered by this prospectus has been passed
upon by Hale and Dorr LLP.

                                     EXPERTS

         The consolidated balance sheets of BioTransplant Incorporated as of
December 31, 1999 and 2000 and the related consolidated statements of
operations, stockholders' equity (deficit) and cash flows for each of the
years in the three-year period ended December 31, 2000 and for the period
from inception (March 20, 1990) to December 31, 2000, incorporated by
reference in this registration statement have been audited by Arthur Andersen
LLP, independent public accountants, as indicated in their report with
respect thereto, and are included herein in reliance upon the authority of
said firm as experts in auditing and accounting.

         The audited historical financial statements of Eligix, Inc. as of
December 31, 2000 and 1999 and for each of the three years in the period
ended December 31, 2000 and for the period from inception (December 27, 1996)
to December 31, 2000 incorporated by reference in this registration statement
to the BioTransplant Incorporated Form 8-K/A dated May 15, 2001, have been so
incorporated in reliance on the report (which contains an explanatory
paragraph relating to Eligix, Inc.'s ability to continue as a going concern
as described in Note A to the financial statements) of PricewaterhouseCoopers
LLP, independent accountants, given on the authority of said firm as experts
in auditing and accounting.

                       WHERE YOU CAN FIND MORE INFORMATION

         We file reports, proxy statements and other documents with the SEC. You
may read and copy any document we file at the SEC's public reference room at
Judiciary Plaza Building, 450 Fifth Street, N.W., Room 1024, Washington, D.C.
20549. You should call 1-800-SEC-0330 for more information on the public
reference room. Our SEC filings are also available to you on the SEC's Internet
site at http://www.sec.gov.

         This prospectus is part of a registration statement that we filed with
the SEC. The registration statement contains more information than this
prospectus regarding us and our common stock, including certain exhibits and
schedules. You can obtain a copy of the registration statement from the SEC at
the address listed above or from the SEC's Internet site.

                                    -16-




                 INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

         The SEC requires us to "incorporate" into this prospectus information
that we file with the SEC in other documents. This means that we can disclose
important information to you by referring to other documents that contain that
information. The information incorporated by reference is considered to be part
of this prospectus. Information contained in this prospectus and information
that we file with the SEC in the future and incorporate by reference in this
prospectus automatically updates and supersedes previously filed information. We
incorporate by reference the documents listed below and any future filings we
make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities
Exchange Act of 1934, prior to the sale of all the shares covered by this
prospectus.

         (1)      Our Annual Report on Form 10-K for the year ended December 31,
                  2000, as amended by Amendment No. 1 to Form 10-K/A and
                  Amendment No. 2 to Form 10-K/A;

         (2)      Our Quarterly Report on Form 10-Q for the quarter ended
                  March 31, 2001, as amended by Amendment No. 1 to Form
                  10-Q/A;

         (3)      Our Quarterly Report on Form 10-Q for the quarter ended
                  June 30, 2001;

         (4)      Our Current Reports on Form 8-K filed on February 21, 2001,
                  February 23, 2001, March 9, 2001, March 12, 2001, May 25,
                  2001 and June 14, 2001;

         (5)      Our Current Report on Form 8-K/A filed on June 26, 2001;

         (6)      The description of our common stock contained in our
                  registration statement on Form 8-A filed with the SEC on
                  April 26, 1996, as amended by a Current Report on Form 8-K
                  filed on August 9, 2000 and including any other amendments
                  or reports filed for the purpose of updating that
                  description.

         You may request a copy of these documents, which will be provided to
you at no cost, by writing or telephoning us using the following contact
information:

                           BioTransplant Incorporated
                           Building 75, Third Avenue
                           Charlestown Navy Yard
                           Charlestown, Massachusetts 02129
                           Attention:  Richard V. Capasso
                           Telephone:  (617) 241-5200

                                    -17-



                                     PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

     ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

     The registrant is subject to the informational and reporting requirements
of Sections 13(a), 14, and 15(d) of the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), and in accordance therewith files reports, proxy
statements and other information with the Securities and Exchange Commission
(the "Commission"). The following documents, which are on file with the
Commission, are incorporated in this registration statement by reference:

     (a) The registrant's latest annual report filed pursuant to Section 13(a)
or 15(d) of the Exchange Act or the latest prospectus filed pursuant to Rule
424(b) under the Securities Act that contains audited financial statements for
the registrant's latest fiscal year for which such statements have been filed.

     (b) All other reports filed pursuant to Section 13(a) or 15(d) of the
Exchange Act since the end of the fiscal year covered by the document referred
to in (a) above.

     (c) The description of the securities contained in the registrant's
registration statement on Form 8-A filed under the Exchange Act, including any
amendment or report filed for the purpose of updating such description.

     All documents subsequently filed by the registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of a
post-effective amendment which indicates that all securities offered hereby have
been sold or which deregisters all securities then remaining unsold, shall be
deemed to be incorporated by reference in this registration statement and to be
part hereof from the date of the filing of such documents. Any statement
contained in a document incorporated or deemed to be incorporated by reference
herein shall be deemed to be modified or superseded for the purposes of this
registration statement to the extent that a statement contained herein or in any
other subsequently filed document which also is or is deemed to be incorporated
by reference herein modifies or supersedes such statement. Any statement so
modified or superseded shall not be deemed, except as so modified or superseded,
to constitute a part of this registration statement.

     ITEM 4. DESCRIPTION OF SECURITIES.

     Not applicable.

     ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Hale and Dorr LLP has opined as to the legality of the securities being
offered by this registration statement. Steven D. Singer, a partner of Hale and
Dorr LLP, serves as Secretary to the registrant.

     ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Article IX of the Company's Restated Certificate of Incorporation provides
that no director of the Company shall be personally liable for any monetary
damages for any breach of fiduciary duty as a director, except to the extent
that the Delaware General Corporation Law prohibits the elimination or
limitation of liability of directors for breach of fiduciary duty.

     Article X of the Company's Restated Certificate of Incorporation provides
that a director or officer of the Company (a) shall be indemnified by the
Company against all expenses (including attorneys' fees), judgments, fines, and
amounts paid in settlement incurred in connection with any litigation or other
legal proceeding (other than an action by or in the right of the Company)
brought against him by virtue of his position as a director or officer of the
Company if he acted in good faith and in a manner he reasonably believed to be
in, or not opposed to, the best interests of the Company, and, with respect to
any criminal action or proceeding, had no reasonable cause to believe his
conduct was unlawful and (b) shall be indemnified by the Company against all
expenses (including attorneys' fees) and amounts paid in settlement incurred in
connection with any action by or in the right of the Company brought against him
by virtue of his position as a director or officer of the Company if he acted in
good faith and in a manner he reasonably believed to be in, or not opposed to,
the best interests of the Company, except that no indemnification shall be made
with respect to any matter as to which such person shall have been adjudged to
be liable to the Company, unless a court determines that, despite such
adjudication but in view of all of the circumstances, he is entitled to
indemnification of such expenses. Notwithstanding the foregoing, to the extent
that a director or officer has been successful, on the merits or otherwise, he
will be indemnified by the Company against all expenses (including attorneys'
fees) incurred in connection therewith. Expenses shall be advanced to a director
or officer at his request, provided that he undertakes to repay the amount
advanced if it is ultimately determined that he is not entitled to
indemnification for such expenses.

     Indemnification is required to be made unless the Company determines that
the applicable standard of conduct required for indemnification has not been
met. In the event of a determination by the Company that the director or officer
did not meet the applicable standard of conduct required for indemnification, or
if the Company fails to make an indemnification payment within 60 days after
such payment is claimed by such person, such person is permitted to petition the
court to make an independent determination as to whether such person is entitled
to indemnification. As a condition precedent to the right of indemnification,
the director or officer must give the Company notice of the action for which
indemnity is sought and the Company has the right to participate in such action
or assume the defense thereof.

     Article X of the Company's Restated Certificate of Incorporation further
provides that the indemnification provided therein is not exclusive, and
provides that in the event that the Delaware General Corporation Law is amended
to expand the indemnification permitted to directors or officers the Company
must indemnify those persons to the fullest extent permitted by such law as so
amended.

                                    -18-




     Section 102 of the Delaware General Corporation law allows a corporation
to eliminate the personal liability of directors of a corporation to the
corporation or its stockholders for monetary damages for a breach of
fiduciary as a director, except where the director breached his duty of
loyalty, failed to act in good faith, engaged in intentional misconduct or
knowingly violated a law, authorized the payment of a dividend or approved a
stock repurchase in violation of Delaware corporate law or obtained an
improper personal benefit. BioTransplant has included such a provision in its
Certificate of Incorporation.

     Section 145 of the Delaware General Corporation Law provides that a
corporation has the power to indemnify a director, officer, employee, or agent
of the corporation and certain other persons serving at the request of the
corporation in related capacities against amounts paid and expenses incurred in
connection with an action or proceeding to which he is or is threatened to be
made a party by reason of such position, if such person shall have acted in good
faith and in a manner he reasonably believed to be in or not opposed to the best
interests of the corporation, and, in any criminal proceeding, if such person
had no reasonable cause to believe his conduct was unlawful; provided that, in
the case of actions brought by or in the right of the corporation, no
indemnification shall be made with respect to any matter as to which such person
shall have been adjudged to be liable to the corporation unless and only to the
extent that the adjudicating court determines that such indemnification is
proper under the circumstances.

     The Company maintains a general liability insurance policy which covers
certain liabilities of directors and officers of the Company arising out of
claims based on acts or omissions in their capacities as directors or officers.

     ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

     Not applicable.

     ITEM 8. EXHIBITS.

     The Exhibit Index immediately preceding the exhibits is incorporated herein
by reference.

     ITEM 9. UNDERTAKINGS.

     1. ITEM 512(a) OF REGULATION S-K. The undersigned registrant hereby
undertakes:

          (1) To file, during any period in which offers or sales are being
     made, a post-effective amendment to this registration statement:

               (i) To include any prospectus required by Section 10(a)(3) of the
          Securities Act;

               (ii) To reflect in the prospectus any facts or events arising
          after the effective date of the registration statement (or the most
          recent post-effective amendment thereof) which, individually or in the
          aggregate, represent a fundamental change in the information set forth
          in the registration statement; and

               (iii) To include any material information with respect to the
          plan of distribution not previously disclosed in the registration
          statement or any material change to such information in the
          registration statement;

          PROVIDED, HOWEVER, that paragraphs (i) and (ii) do not apply if the
          information required to be included in a post-effective amendment by
          those paragraphs is contained in periodic reports filed with or
          furnished to the Commission by the registrant pursuant to Section 13
          or Section 15(d) of the Exchange Act that are incorporated by
          reference in the registration statement.

                                    -19-




          (2) That, for the purpose of determining any liability under the
     Securities Act, each such post-effective amendment shall be deemed to be a
     new registration statement relating to the securities offered therein, and
     the offering of such securities at that time shall be deemed to be the
     initial BONA FIDE offering thereof.

          (3) To remove from registration by means of a post-effective amendment
     any of the securities being registered which remain unsold at the
     termination of the offering.

     2. ITEM 512(b) OF REGULATION S-K. The undersigned registrant hereby
undertakes that, for purposes of determining any liability under the Securities
Act, each filing of the registrant's annual report pursuant to Section 13(a) or
Section 15(d) of the Exchange Act that is incorporated by reference in the
registration statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial BONA FIDE offering thereof.

     3. ITEM 512(h) OF REGULATION S-K. Insofar as indemnification for
liabilities arising under the Securities Act may be permitted to directors,
officers and controlling persons of the registrant pursuant to the foregoing
provisions, or otherwise, the registrant has been advised that in the opinion of
the Securities and Exchange Commission such indemnification is against public
policy as expressed in the Securities Act and is, therefore, unenforceable. In
the event that a claim for indemnification against such liabilities (other than
the payment by the registrant of expenses incurred or paid by a director,
officer or controlling person of the registrant in the successful defense of any
action, suit or proceeding) is asserted by such director, officer or controlling
person in connection with the securities being registered, the registrant will,
unless in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the
Securities Act and will be governed by the final adjudication of such issue.

                                    -20-





                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in Charlestown, Massachusetts, on this 26th day of September, 2001.

                                       BIOTRANSPLANT INCORPORATED

                                       By: /s/ Richard V. Capasso
                                          -------------------------------------
                                          Richard V. Capasso
                                          Vice President, Finance
                                          and Treasurer

     Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed by the following persons in the
capacities and on the dates indicated.



       SIGNATURE                                TITLE                             DATE
                                                                       

  Elliot Lebowitz*                    Chief Executive Officer
-------------------------             and Director
Elliot Lebowitz                       (Principal executive officer)          September 26, 2001

    Walter C. Ogier*
-------------------------             President, Chief Operating
Walter C. Ogier                       Officer and Director                   September 26, 2001

/s/ Richard V. Capasso                Vice President, Finance and
-------------------------             Treasurer (Principal financial
Richard V. Capasso                    and accounting officer)                September 26, 2001

    James C. Foster*
-------------------------
James C. Foster                       Director                               September 26, 2001


-------------------------
Daniel O. Hauser                      Director


                                    -21-






       SIGNATURE                                TITLE                             DATE
                                                                      

    Arnold L. Oronsky*
-------------------------
Arnold L. Oronsky                     Director                              September 26, 2001

    Michael S. Perry*
-------------------------
Michael S. Perry                      Director                              September 26, 2001

    Susan M. Racher*
-------------------------
Susan M. Racher                       Director                              September 26, 2001

* /s/ Richard V. Capasso
-------------------------
Richard V. Capasso
Attorney-in-fact



                                    -22-








                                INDEX TO EXHIBITS

NUMBER     DESCRIPTION
4.1(1)     Restated Certificate of Incorporation of the Registrant, as amended
           to date
4.2(2)     By-Laws of the Registrant, as amended to date
5.1*       Opinion of Hale and Dorr LLP, counsel to the Registrant
23.1*      Consent of Hale and Dorr LLP (included in Exhibit 5.1)
23.2       Consent of Arthur Andersen LLP
23.3       Consent of PricewaterhouseCoopers LLP
24.1*      Power of attorney

------------
(1) Incorporated herein by reference from the Registrant's Form 8-K dated
    July 18, 2000 (File No. 000-28324).
(2) Incorporated herein by reference to the Registrant's Registration Statement
    on Form S-1, as amended (File No. 333-02144).
*   Previously filed.

                                    -23-