PAGE 1 000 A000000 01/31/2008 000 C000000 0001093428 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 SENIOR INCOME FUND 001 B000000 811-09571 001 C000000 3129177700 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 008 A000002 SYMPHONY ASSET MANAGEMENT, LLC 008 B000002 S 008 C000002 801-52638 008 D010002 SAN FRANCISCO 008 D020002 CA 008 D030002 94104 012 A000001 EQUISERVE INC. 012 B000001 84-05925 012 C010001 PROVIDENCE 012 C020001 RI 012 C030001 02940 PAGE 2 013 A000001 ERNST & YOUNG LLP 013 B010001 CHICAGO 013 B020001 IL 013 B030001 60606 013 B040001 6301 014 A000001 NUVEEN INVESTMENTS, LLC 014 B000001 8-13464 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 184 019 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 UBS 022 B000001 13-2638166 022 C000001 5945 022 D000001 1908 022 A000002 BANK OF AMERICA 022 B000002 56-2058405 022 C000002 5723 022 D000002 1980 022 A000003 CITIGROUP 022 B000003 13-3214963 022 C000003 5859 022 D000003 0 022 A000004 GOLDMAN SACHS 022 B000004 13-5108880 022 C000004 1920 022 D000004 2985 022 A000005 JP MORGAN CHASE 022 B000005 13-3224016 022 C000005 3611 022 D000005 0 022 A000006 ITG 022 B000006 95-2848406 022 C000006 3534 PAGE 3 022 D000006 0 022 A000007 ROYAL BANK OF SCOTLAND 022 B000007 13-4187851 022 C000007 3416 022 D000007 0 022 A000008 CREDIT SUISSE 022 B000008 13-5659485 022 C000008 2880 022 D000008 0 022 A000009 BARCLAYS BANK PLC 022 B000009 13-4942190 022 C000009 1985 022 D000009 0 022 A000010 MERRILL LYNCH 022 B000010 13-5674085 022 C000010 1920 022 D000010 0 023 C000000 40429 023 D000000 6873 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 PAGE 4 028 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 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 PAGE 5 048 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 Y 053 A000000 Y 053 B000000 Y 053 C000000 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 N 060 B000000 N 061 000000 0 062 A000000 Y 062 B000000 0.0 062 C000000 0.0 062 D000000 14.6 062 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 4.5 062 Q000000 152.8 062 R000000 0.7 063 A000000 0 063 B000000 12.8 064 A000000 Y 064 B000000 N 066 A000000 N 067 000000 N 068 A000000 N 068 B000000 N 069 000000 N 070 A010000 Y 070 A020000 Y 070 B010000 Y 070 B020000 N 070 C010000 Y 070 C020000 N 070 D010000 Y 070 D020000 N 070 E010000 Y 070 E020000 N 070 F010000 Y 070 F020000 N 070 G010000 Y 070 G020000 N 070 H010000 Y 070 H020000 N 070 I010000 N 070 I020000 N 070 J010000 Y 070 J020000 Y 070 K010000 Y 070 K020000 N 070 L010000 Y 070 L020000 N 070 M010000 N 070 M020000 N 070 N010000 Y 070 N020000 N 070 O010000 Y 070 O020000 N 070 P010000 N 070 P020000 N 070 Q010000 N PAGE 7 070 Q020000 N 070 R010000 N 070 R020000 N 071 A000000 83304 071 B000000 95060 071 C000000 367417 071 D000000 23 072 A000000 6 072 B000000 15857 072 C000000 835 072 D000000 0 072 E000000 222 072 F000000 1615 072 G000000 0 072 H000000 0 072 I000000 5 072 J000000 115 072 K000000 0 072 L000000 37 072 M000000 5 072 N000000 0 072 O000000 0 072 P000000 3150 072 Q000000 0 072 R000000 23 072 S000000 10 072 T000000 0 072 U000000 0 072 V000000 0 072 W000000 106 072 X000000 5066 072 Y000000 242 072 Z000000 12090 072AA000000 0 072BB000000 131 072CC010000 0 072CC020000 19782 072DD010000 10800 072DD020000 0 072EE000000 0 073 A010000 0.3620 073 A020000 0.0000 073 B000000 0.0000 073 C000000 0.0000 074 A000000 0 074 B000000 31908 074 C000000 0 074 D000000 344869 074 E000000 0 074 F000000 1323 074 G000000 0 PAGE 8 074 H000000 0 074 I000000 134 074 J000000 43 074 K000000 0 074 L000000 3264 074 M000000 92 074 N000000 381633 074 O000000 10642 074 P000000 235 074 Q000000 0 074 R010000 0 074 R020000 0 074 R030000 0 074 R040000 105579 074 S000000 46000 074 T000000 219177 074 U010000 29834 074 U020000 0 074 V010000 7.35 074 V020000 0.00 074 W000000 0.0000 074 X000000 159 074 Y000000 29812 075 A000000 0 075 B000000 236004 076 000000 7.15 077 A000000 Y 077 C000000 Y 077 Q010000 Y 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 0 086 D020000 0 086 E010000 0 086 E020000 0 086 F010000 0 086 F020000 0 087 A010000 COMMON STOCK 087 A020000 67067Y104 087 A030000 NSL 088 A000000 N PAGE 9 088 B000000 N 088 C000000 N 088 D000000 Y SIGNATURE STEPHEN D. FOY TITLE V.P. & CONTROLLER