PAGE 1 000 B000000 12/31/2004 000 C000000 0000831655 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 PARTICIPATION INVESTORS 001 B000000 811-5531 001 C000000 4132261000 002 A000000 1500 MAIN STREET, SUITE 600 002 B000000 SPRINGFIELD 002 C000000 MA 002 D010000 01115 002 D020000 0001 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 0001 012 A000001 SHAREHOLDER FINANCIAL SERVICES, INC. 012 B000001 84-1817 012 C010001 DENVER 012 C020001 CO 012 C030001 80217 012 C040001 3673 013 A000001 KPMG LLP 013 B010001 BOSTON 013 B020001 MA 013 B030001 02110 013 B040001 2371 PAGE 2 015 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 13-6176976 020 C000001 1 020 A000002 LAZARD FRERES AND CO 020 B000002 13-5545100 020 C000002 1 020 A000003 FIRST BOSTON CORP. 020 B000003 13-5659485 020 C000003 1 020 A000004 PRUDENTIAL SECURITIES INC. 020 B000004 22-2347336 020 C000004 0 020 A000005 SPEAR LEEDS & KELLOGG, LP 020 B000005 13-5515460 020 C000005 0 020 A000006 J.P. MORGAN CHASE 020 B000006 13-4994650 020 C000006 0 020 A000007 CHARLES SCHWAB 020 B000007 94-1737782 020 C000007 0 020 A000008 MERRILL, LYNCH, PIERCE, FENNER & SMITH INC. 020 B000008 13-5674085 020 C000008 0 020 A000009 GOLDMAN, SACHS & CO. 020 B000009 13-5108880 020 C000009 0 020 A000010 KNIGHT SECURITIES 020 B000010 22-3660471 020 C000010 0 021 000000 5 022 A000001 JP MORGAN CHASE 022 B000001 13-4994650 022 C000001 82399 022 D000001 750 022 A000002 GOLDMAN, SACHS & CO. 022 B000002 13-5108880 022 C000002 80973 022 D000002 1050 022 A000003 MERRILL, LYNCH, PIERCE, FENNER & SMITH INC. 022 B000003 13-5674085 PAGE 3 022 C000003 68299 022 D000003 191 022 A000004 FIRST BOSTON CORP. 022 B000004 13-5659485 022 C000004 39824 022 D000004 1471 022 A000005 SHEARSON LEHMAN AMER EXP 022 B000005 13-2518466 022 C000005 24211 022 D000005 713 022 A000006 FIRST CHICAGO CAPITAL MARKET 022 B000006 36-3595942 022 C000006 8264 022 D000006 0 022 A000007 JEFFERIES & CO., INC. 022 B000007 94-1737782 022 C000007 3190 022 D000007 2031 022 A000008 SALOMON SMITH BARNEY HOLD INC. 022 B000008 11-2418191 022 C000008 3496 022 D000008 1448 022 A000009 KBC FINANCIAL SERVICES 022 B000009 13-4035459 022 C000009 272 022 D000009 4272 022 A000010 HKW & COMPANY 022 B000010 13-1769063 022 C000010 4125 022 D000010 0 023 C000000 325562 023 D000000 19465 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 PAGE 4 028 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 0 028 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 PAGE 5 047 000000 Y 048 000000 0.900 048 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 051 000000 N 052 000000 N 053 A000000 N 054 A000000 Y 054 B000000 Y 054 C000000 Y 054 D000000 N 054 E000000 N 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 Y 055 B000000 Y 056 000000 Y 057 000000 N 058 A000000 N 059 000000 Y 060 A000000 Y PAGE 6 060 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 5.2 062 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 93.4 062 Q000000 0.0 062 R000000 21.1 063 A000000 0 063 B000000 5.6 064 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 PAGE 7 070 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 070 N010000 Y 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 60888 071 B000000 57779 071 C000000 112730 071 D000000 51 072 A000000 12 072 B000000 10936 072 C000000 1322 072 D000000 0 072 E000000 0 072 F000000 919 072 G000000 0 072 H000000 0 072 I000000 21 072 J000000 24 072 K000000 0 072 L000000 80 072 M000000 105 072 N000000 0 072 O000000 159 072 P000000 903 072 Q000000 0 072 R000000 50 072 S000000 236 072 T000000 0 072 U000000 0 072 V000000 0 072 W000000 48 072 X000000 2545 072 Y000000 0 072 Z000000 9713 PAGE 8 072AA000000 20692 072BB000000 11236 072CC010000 12494 072CC020000 0 072DD010000 10613 072DD020000 0 072EE000000 0 073 A010000 1.1000 073 A020000 0.0000 073 B000000 0.0000 073 C000000 0.0000 074 A000000 2370 074 B000000 0 074 C000000 5580 074 D000000 100452 074 E000000 4941 074 F000000 13622 074 G000000 0 074 H000000 0 074 I000000 4176 074 J000000 1529 074 K000000 0 074 L000000 1867 074 M000000 0 074 N000000 134537 074 O000000 0 074 P000000 242 074 Q000000 22500 074 R010000 0 074 R020000 0 074 R030000 0 074 R040000 4185 074 S000000 0 074 T000000 107610 074 U010000 9672559 074 U020000 0 074 V010000 11.13 074 V020000 0.00 074 W000000 0.0000 074 X000000 7199 074 Y000000 0 075 A000000 0 075 B000000 101130 076 000000 13.31 077 A000000 Y 077 B000000 Y 077 E000000 Y 077 O000000 Y 077 Q010000 Y 077 Q020000 N 077 Q030000 N PAGE 9 078 000000 N 080 A000000 NATIONAL UNION FIRE INS.CO. OF PITTSBURGH, PA 080 C000000 1200 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 82 086 A020000 927 086 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 SHARES OF BENEFICIAL INTEREST 087 A020000 576299101 087 A030000 MPV 088 A000000 Y 088 B000000 N 088 C000000 N 088 D000000 N SIGNATURE CHARLES C. MCCOBB, JR. TITLE V.P. AND C.F.O. EXHIBIT INDEX TO FORM N-SAR OF MASSMUTUAL PARTICIPATION INVESTORS FOR SEMI-ANNUAL PERIOD ENDED DECEMBER 31, 2004 EXHIBIT NO. DESCRIPTION 77B Accountant's Report on Internal Control 77E Legal Proceedings 77O Transactions Effected Pursuant to Rule 10f-3