PAGE 1
000 A000000 04/30/2009
000 C000000 0000878242
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 6.1
000 J000000 A
001 A000000 NUVEEN INSURED MUNI OPPORTUNITY FUND, INC.
001 B000000 811-06379
001 C000000 3129178200
002 A000000 333 WEST WACKER DRIVE
002 B000000 CHICAGO
002 C000000 IL
002 D010000 60606
002 D020000 1286
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 N
007 B000000 0
007 C010100 1
007 C010200 2
007 C010300 3
007 C010400 4
007 C010500 5
007 C010600 6
007 C010700 7
007 C010800 8
007 C010900 9
007 C011000 10
008 A000001 NUVEEN ASSET MANAGEMENT
008 B000001 A
008 C000001 801-14147
008 D010001 CHICAGO
008 D020001 IL
008 D030001 60606
008 D040001 1286
012 A000001 EQUISERVE INC.
012 B000001 84-05925
012 C010001 PROVIDENCE
012 C020001 RI
012 C030001 02940
013 A000001 ERNST & YOUNG LLP
013 B010001 CHICAGO
013 B020001 IL
013 B030001 60606
014 A000001 NUVEEN INVESTMENTS, LLC
014 B000001 8-13464
PAGE 2
015 A000001 STATE STREET BANK AND TRUST COMPANY
015 B000001 C
015 C010001 BOSTON
015 C020001 MA
015 C030001 02110
015 E010001 X
018 000000 Y
019 A000000 Y
019 B000000 200
019 C000000 NUVEENFUND
020 C000001 0
020 C000002 0
020 C000003 0
020 C000004 0
020 C000005 0
020 C000006 0
020 C000007 0
020 C000008 0
020 C000009 0
020 C000010 0
021 000000 0
022 A000001 JP MORGAN CHASE
022 B000001 13-3224016
022 C000001 11878
022 D000001 18181
022 A000002 MORGAN STANLEY
022 B000002 13-2655998
022 C000002 10409
022 D000002 14978
022 A000003 BARCLAYS BANK PLC
022 B000003 13-4942190
022 C000003 13821
022 D000003 8776
022 A000004 CITIGROUP
022 B000004 13-3214963
022 C000004 16805
022 D000004 573
022 A000005 GOLDMAN SACHS
022 B000005 13-5108880
022 C000005 11863
022 D000005 0
022 A000006 BANK OF AMERICA
022 B000006 56-2058405
022 C000006 6154
022 D000006 0
022 A000007 WEDBUSH MORGAN
022 B000007 95-2495390
022 C000007 0
022 D000007 5666
022 C000008 0
022 D000008 0
PAGE 3
022 C000009 0
022 D000009 0
022 C000010 0
022 D000010 0
023 C000000 70929
023 D000000 48174
024 000000 N
025 D000001 0
025 D000002 0
025 D000003 0
025 D000004 0
025 D000005 0
025 D000006 0
025 D000007 0
025 D000008 0
026 A000000 N
026 B000000 N
026 C000000 N
026 D000000 Y
026 E000000 N
026 F000000 N
026 G010000 N
026 G020000 N
026 H000000 N
027 000000 N
028 A010000 0
028 A020000 0
028 A030000 0
028 A040000 0
028 B010000 0
028 B020000 0
028 B030000 0
028 B040000 0
028 C010000 0
028 C020000 0
028 C030000 0
028 C040000 0
028 D010000 0
028 D020000 0
028 D030000 0
028 D040000 0
028 E010000 0
028 E020000 0
028 E030000 0
028 E040000 0
028 F010000 0
028 F020000 0
028 F030000 0
028 F040000 0
028 G010000 0
028 G020000 0
PAGE 4
028 G030000 0
028 G040000 0
028 H000000 0
030 A000000 0
030 B000000 0.00
030 C000000 0.00
031 A000000 0
031 B000000 0
032 000000 0
033 000000 0
035 000000 0
036 B000000 0
038 000000 0
042 A000000 0
042 B000000 0
042 C000000 0
042 D000000 0
042 E000000 0
042 F000000 0
042 G000000 0
042 H000000 0
043 000000 0
044 000000 0
045 000000 Y
046 000000 N
047 000000 N
048 000000 0.000
048 A010000 0
048 A020000 0.000
048 B010000 0
048 B020000 0.000
048 C010000 0
048 C020000 0.000
048 D010000 0
048 D020000 0.000
048 E010000 0
048 E020000 0.000
048 F010000 0
048 F020000 0.000
048 G010000 0
048 G020000 0.000
048 H010000 0
048 H020000 0.000
048 I010000 0
048 I020000 0.000
048 J010000 0
048 J020000 0.000
048 K010000 0
048 K020000 0.000
049 000000 N
050 000000 N
PAGE 5
051 000000 N
052 000000 Y
053 A000000 N
054 A000000 Y
054 B000000 N
054 C000000 N
054 D000000 N
054 E000000 N
054 F000000 N
054 G000000 N
054 H000000 Y
054 I000000 N
054 J000000 Y
054 K000000 N
054 L000000 N
054 M000000 Y
054 N000000 N
054 O000000 Y
055 A000000 N
055 B000000 N
056 000000 Y
057 000000 N
058 A000000 N
059 000000 Y
060 A000000 Y
060 B000000 Y
061 000000 0
062 A000000 Y
062 B000000 0.0
062 C000000 0.0
062 D000000 0.0
062 E000000 0.9
062 F000000 0.0
062 G000000 0.0
062 H000000 0.0
062 I000000 0.0
062 J000000 0.0
062 K000000 0.0
062 L000000 0.0
062 M000000 0.0
062 N000000 0.0
062 O000000 160.5
062 P000000 0.0
062 Q000000 0.0
062 R000000 0.0
063 A000000 0
063 B000000 10.5
064 A000000 Y
064 B000000 N
066 A000000 N
067 000000 N
PAGE 6
068 A000000 N
068 B000000 N
069 000000 N
070 A010000 Y
070 A020000 N
070 B010000 N
070 B020000 N
070 C010000 Y
070 C020000 N
070 D010000 N
070 D020000 N
070 E010000 Y
070 E020000 N
070 F010000 N
070 F020000 N
070 G010000 Y
070 G020000 N
070 H010000 N
070 H020000 N
070 I010000 N
070 I020000 N
070 J010000 Y
070 J020000 N
070 K010000 N
070 K020000 N
070 L010000 N
070 L020000 N
070 M010000 N
070 M020000 N
070 N010000 N
070 N020000 N
070 O010000 Y
070 O020000 N
070 P010000 N
070 P020000 N
070 Q010000 N
070 Q020000 N
070 R010000 N
070 R020000 N
071 A000000 61879
071 B000000 86973
071 C000000 1710081
071 D000000 4
072 A000000 6
072 B000000 46578
072 C000000 0
072 D000000 0
072 E000000 0
072 F000000 5026
072 G000000 0
072 H000000 0
PAGE 7
072 I000000 86
072 J000000 69
072 K000000 58
072 L000000 117
072 M000000 33
072 N000000 0
072 O000000 0
072 P000000 635
072 Q000000 0
072 R000000 34
072 S000000 42
072 T000000 0
072 U000000 0
072 V000000 0
072 W000000 862
072 X000000 6962
072 Y000000 0
072 Z000000 39616
072AA000000 0
072BB000000 1202
072CC010000 81420
072CC020000 0
072DD010000 28404
072DD020000 0
072EE000000 0
073 A010000 0.3550
073 A020000 0.0000
073 B000000 0.0000
073 C000000 0.0000
074 A000000 16926
074 B000000 0
074 C000000 10215
074 D000000 1753935
074 E000000 0
074 F000000 0
074 G000000 0
074 H000000 0
074 I000000 0
074 J000000 135
074 K000000 0
074 L000000 28211
074 M000000 356
074 N000000 1809778
074 O000000 3799
074 P000000 844
074 Q000000 0
074 R010000 0
074 R020000 0
074 R030000 0
074 R040000 138989
074 S000000 573300
PAGE 8
074 T000000 1092846
074 U010000 1092846
074 U020000 0
074 V010000 13.47
074 V020000 0.00
074 W000000 0.0000
074 X000000 3970
074 Y000000 275471
075 A000000 0
075 B000000 1040689
076 000000 12.15
077 A000000 N
078 000000 N
080 C000000 0
081 B000000 0
082 B000000 0
083 B000000 0
084 B000000 0
086 A010000 0
086 A020000 0
086 B010000 0
086 B020000 0
086 C010000 0
086 C020000 0
086 D010000 2
086 D020000 50050
086 E010000 0
086 E020000 0
086 F010000 0
086 F020000 0
087 A010000 COMMON STOCK
087 A020000 670984103
087 A030000 NIO
088 A000000 N
088 B000000 N
088 C000000 N
088 D000000 Y
SIGNATURE STEPHEN D. FOY
TITLE V.P. & CONTROLLER