PAGE 1
000 B000000 12/31/2009
000 C000000 0000275694
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 6.1
000 J000000 A
001 A000000 MASSMUTUAL CORPORATE INVESTORS
001 B000000 811-2183
001 C000000 4132261000
002 A000000 1500 MAIN STREET, P.O. BOX 15189
002 B000000 SPRINGFIELD
002 C000000 MA
002 D010000 01115
002 D020000 5189
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 BABSON CAPITAL MANAGEMENT LLC
008 B000001 A
008 C000001 801-241
008 D010001 SPRINGFIELD
008 D020001 MA
008 D030001 01115
008 D040001 5189
012 A000001 SHAREHOLDER FINANCIAL SERVICES, INC.
012 B000001 84-1817
012 C010001 CENTENNIAL
012 C020001 CO
012 C030001 80112
013 A000001 KPMG LLP
013 B010001 BOSTON
013 B020001 MA
013 B030001 02110
013 B040001 2371
014 A000001 BABSON CAPITAL SECURITIES INC
PAGE 2
014 B000001 8-47589
014 A000002 MML INVESTOR SERVICES, INC.
014 B000002 8-27250
014 A000003 OPPENHEIMER DISTRIBUTOR, INC.
014 B000003 8-22992
014 A000004 MML DISTRIBUTORS, LLC
014 B000004 8-48203
015 A000001 CITIBANK, N.A.
015 B000001 C
015 C010001 NEW YORK
015 C020001 NY
015 C030001 10043
015 E010001 X
018 000000 Y
019 A000000 Y
019 B000000 2
019 C000000 CIPIINVEST
020 A000001 ALLEN & CO.
020 B000001 13-4132953
020 C000001 1
020 A000002 FIRST BOSTON CORP.
020 B000002 13-5659485
020 C000002 3
020 A000003 JP MORGAN CHASE
020 B000003 13-4994650
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 1
022 A000001 BA SECURITIES INC
022 B000001 23-3069627
022 C000001 65067
022 D000001 7477
022 A000002 JP MORGAN CHASE
022 B000002 13-4994650
022 C000002 19838
022 D000002 6891
022 A000003 GOLDMAN, SACHS & CO
022 B000003 13-5108880
022 C000003 42441
022 D000003 1800
022 A000004 BARCLAYS CAPITAL INC.
022 C000004 19187
022 D000004 8262
022 A000005 CITIGROUP
022 B000005 13-3214963
PAGE 3
022 C000005 11833
022 D000005 586
022 A000006 FIRST BOSTON CORP
022 B000006 13-5659485
022 C000006 10788
022 D000006 1674
022 A000007 SUNTRUST CAPITAL MARKET
022 C000007 7219
022 D000007 0
022 A000008 WACHOVIA SECURITIES LLC
022 B000008 34-1542819
022 C000008 1739
022 D000008 5547
022 A000009 WEXLER VIDEO LLC
022 C000009 2786
022 D000009 0
022 A000010 HKW & CO.
022 C000010 3166
022 D000010 0
023 C000000 211216
023 D000000 61871
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 Y
026 C000000 N
026 D000000 Y
026 E000000 N
026 F000000 Y
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
PAGE 4
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
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 Y
048 000000 1.250
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
PAGE 5
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
051 000000 N
052 000000 N
053 A000000 N
054 A000000 Y
054 B000000 Y
054 C000000 Y
054 D000000 N
054 E000000 Y
054 F000000 N
054 G000000 Y
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 0.0
062 F000000 0.0
062 G000000 0.0
062 H000000 0.0
062 I000000 0.0
PAGE 6
062 J000000 0.0
062 K000000 0.0
062 L000000 0.0
062 M000000 0.0
062 N000000 0.0
062 O000000 0.0
062 P000000 93.5
062 Q000000 0.0
062 R000000 14.0
063 A000000 0
063 B000000 5.0
064 A000000 Y
064 B000000 Y
065 000000 N
066 A000000 Y
066 B000000 N
066 C000000 N
066 D000000 N
066 E000000 N
066 F000000 N
066 G000000 Y
067 000000 N
068 A000000 N
068 B000000 N
069 000000 N
070 A010000 Y
070 A020000 N
070 B010000 Y
070 B020000 Y
070 C010000 N
070 C020000 N
070 D010000 N
070 D020000 N
070 E010000 N
070 E020000 N
070 F010000 N
070 F020000 N
070 G010000 N
070 G020000 N
070 H010000 N
070 H020000 N
070 I010000 N
070 I020000 N
070 J010000 Y
070 J020000 Y
070 K010000 N
070 K020000 N
070 L010000 Y
070 L020000 Y
070 M010000 N
070 M020000 N
PAGE 7
070 N010000 N
070 N020000 N
070 O010000 Y
070 O020000 Y
070 P010000 N
070 P020000 N
070 Q010000 N
070 Q020000 N
070 R010000 N
070 R020000 N
071 A000000 53359
071 B000000 61911
071 C000000 234561
071 D000000 23
072 A000000 12
072 B000000 24032
072 C000000 27
072 D000000 0
072 E000000 32
072 F000000 2643
072 G000000 0
072 H000000 0
072 I000000 23
072 J000000 25
072 K000000 0
072 L000000 120
072 M000000 218
072 N000000 0
072 O000000 0
072 P000000 1584
072 Q000000 0
072 R000000 97
072 S000000 58
072 T000000 0
072 U000000 0
072 V000000 0
072 W000000 153
072 X000000 4921
072 Y000000 0
072 Z000000 19170
072AA000000 10527
072BB000000 9659
072CC010000 0
072CC020000 5286
072DD010000 20169
072DD020000 0
072EE000000 0
073 A010000 2.1600
073 A020000 0.0000
073 B000000 0.0000
073 C000000 0.0000
PAGE 8
074 A000000 17217
074 B000000 0
074 C000000 0
074 D000000 200516
074 E000000 6733
074 F000000 16632
074 G000000 0
074 H000000 0
074 I000000 6679
074 J000000 47
074 K000000 0
074 L000000 3156
074 M000000 0
074 N000000 250980
074 O000000 0
074 P000000 670
074 Q000000 30000
074 R010000 0
074 R020000 0
074 R030000 0
074 R040000 5873
074 S000000 0
074 T000000 214437
074 U010000 9367616
074 U020000 0
074 V010000 22.89
074 V020000 0.00
074 W000000 0.0000
074 X000000 8511
074 Y000000 0
075 A000000 0
075 B000000 211590
076 000000 25.10
077 A000000 Y
077 B000000 Y
077 C000000 N
077 D000000 N
077 E000000 N
077 F000000 N
077 G000000 N
077 H000000 N
077 I000000 N
077 J000000 N
077 K000000 N
077 L000000 N
077 M000000 N
077 N000000 N
077 O000000 Y
077 P000000 N
077 Q010000 N
077 Q020000 Y
PAGE 9
077 Q030000 N
078 000000 N
080 A000000 GREAT AMERICAN INSURANCE GROUP
080 B000000 NONE
080 C000000 1125
081 A000000 Y
081 B000000 1
082 A000000 N
082 B000000 0
083 A000000 N
083 B000000 0
084 A000000 N
084 B000000 0
085 A000000 Y
085 B000000 N
086 A010000 48
086 A020000 1138
086 B010000 0
086 B020000 0
086 C010000 0
086 C020000 0
086 D010000 0
086 D020000 0
086 E010000 0
086 E020000 0
086 F010000 0
086 F020000 0
087 A010000 COMMON SHARES
087 A020000 576292106
087 A030000 MCI
088 A000000 Y
088 B000000 N
088 C000000 N
088 D000000 Y
SIGNATURE JAMES M. ROY
TITLE V.P. AND C.F.O.
EXHIBIT INDEX TO FORM N-SAR
OF MASSMUTUAL CORPORATE INVESTORS
FOR ANNUAL PERIOD ENDED DECEMBER 31, 2009
EXHIBIT NO. DESCRIPTION
77B Accountant's Report on Internal Controls
77O Transactions Effected Pursuant to Rule 10f-3
77Q2 Information Called for by Item 405 of Regulation S-K