Form N-Q

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549

FORM N-Q


QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS OF REGISTERED MANAGEMENT INVESTMENT COMPANY

Investment Company Act file number         811-09571         

        Nuveen Senior Income Fund         
(Exact name of registrant as specified in charter)


        333 West Wacker Drive, Chicago, Illinois 60606         

(Address of principal executive offices) (Zip code)


Jessica R. Droeger—Vice President and Secretary
        333 West Wacker Drive, Chicago, Illinois 60606         

(Name and address of agent for service)

Registrant's telephone number, including area code:         312-917-7700        

Date of fiscal year end:            7/31          

Date of reporting period:          10/31/05         

Form N-Q is to be used by management investment companies, other than small business investment companies registered on Form N-5 (§§ 239.24 and 274.5 of this chapter), to file reports with the Commission, not later than 60 days after the close of the first and third fiscal quarters, pursuant to rule 30b1-5 under the Investment Company Act of 1940 (17 CFR 270.30b1-5). The Commission may use the information provided on Form N-Q in its regulatory, disclosure review, inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-Q, and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form N-Q unless the Form displays a currently valid Office of Management and Budget (“OMB”) control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to the Secretary, Securities and Exchange Commission, 450 Fifth Street, NW, Washington, DC 20549-0609. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. § 3507.

Item 1. Schedule of Investments

  Portfolio of Investments (Unaudited)
Nuveen Senior Income Fund (NSL)
October 31, 2005

      Weighted 
Average 
 Coupon 
         
Principal
 Amount (000) 
Stated 
 Maturity* 
Ratings**    
   
   
  Description(1)    Moody's  S&P  Value 

    VARIABLE RATE SENIOR LOAN INTERESTS(2) - 136.1% (85.0% of total investments)           
    Aerospace & Defense - 2.4% (1.5% of total investments)           
$  2,993  Mid-Western Aircraft Systems Inc., Term Loan B  6.409 %  6/10/11  B1  BB-  $ 3,034,769 
  2,437  Vought Aircraft Industries, Inc., Term Loan  6.590 %  12/22/11  Ba3  B+  2,464,943 
  545  Vought Aircraft Industries, Inc., Tranche B, Letter of Credit  6.364 %  12/22/10  Ba3  B+  552,358 

              6,052,070 

    Airlines - 2.4% (1.5% of total investments)           
  5,925  United Air Lines, Inc., DIP Term Loan (Tranche B) (b)   7.960 %  3/31/06  N/R  N/R  5,997,272 

    Auto Components - 9.6% (6.0% of total investments)           
  2,343  Accuride Corporation, Term Loan  6.177 %  1/31/10  B1  B+  2,361,571 
  4,224  Federal-Mogul Corporation, Term Loan A (b)  6.330 %  2/24/04  N/R  N/R  3,979,381 
  5,551  Federal-Mogul Corporation, Term Loan B (b)  6.580 %  2/24/05  N/R  N/R  5,235,607 
  1,914  GenTek Inc, Term Loan B  6.605 %  12/31/10  B2  B+  1,928,840 
  2,000  Goodyear Tire & Rubber Company, Second Lien Term Loan  7.060 %  4/30/10  B2  B+  2,019,791 
  1,000  Goodyear Tire & Rubber Company, Term Loan  3.764 %  4/30/10  B2  BB  1,008,929 
  3,046  MetalForming Technologies, Inc., Term Loan A (a)(b)  0.000 %  9/30/07  N/R  N/R  1,675,173 
  1,187  MetalForming Technologies, Inc., Term Loan B (PIK) (a)(b)  0.000 %  9/30/07  N/R  N/R  652,942 
  3,042  Tenneco Automotive Inc., Term Loan B  6.080 %  12/12/10  B1  B+  3,092,651 
  1,336  Tenneco Automotive Inc., Term Loan B-1  5.943 %  12/12/10  B1  B+  1,358,547 
  723  United Components, Inc., Term Loan C  6.260 %  6/30/10  B1  BB-  735,088 

              24,048,520 

    Beverages - 3.1% (2.0% of total investments)           
  1,957  Constellation Brands, Inc., Term Loan  5.659 %  11/30/11  Ba2  BB  1,980,549 
  5,802  Dr. Pepper/Seven UP Bottling Group, Inc., Term Loan B  6.158 %  12/19/10  N/R  N/R  5,891,247 

              7,871,796 

    Building Products - 4.0% (2.5% of total investments)           
  2,995  Euramax Holdings Inc., Term Loan B (d)  TBD   TBD  B2  B+  2,973,607 
  1,980  Nortek, Inc., Term Loan B  5.915 %  8/27/11  B2  B  2,003,265 
  2,485  Stile Acquisition Corporation, Canadian Term Loan  5.666 %  3/21/13  B2  BB-  2,479,028 
  2,490  Stile Acquisition Corporation, Term Loan B  6.203 %  5/13/11  B2  BB-  2,483,251 

              9,939,151 

    Chemicals - 5.3% (3.3% of total investments)           
  2,415  Celanese Holdings LLC, Term Loan C  6.313 %  4/06/11  B1  B+  2,453,220 
  876  Huntsman International LLC, Term Loan  5.720 %  8/16/12  Ba3  BB-  881,518 
  3,980  Mosaic Company, Term Loan  5.232 %  2/21/12  Ba2  BB+  4,027,885 
  2,488  PQ Corporation, Term Loan  6.063 %  2/11/12  B1  B+  2,507,711 
  1,990  Rockwood Specialties Group, Inc., Tranche D  6.466 %  7/30/12  B1  B+  2,024,203 
  1,500  Wellman, Inc., First Lien Term Loan  7.710 %  2/10/09  B1  B+  1,528,750 

              13,423,287 

    Commercial Services & Supplies - 5.8% (3.6% of total investments)           
  3,000  Acco Brands, Term Loan B  5.726 %  8/17/10  Ba3  BB-  3,037,875 
  1,472  Allied Waste North America, Inc., Letter of Credit  6.030 %  3/21/12  B1  BB  1,481,330 
  3,895  Allied Waste North America, Inc., Term Loan B  6.038 %  3/12/21  B1  BB  3,920,389 
  3,950  National Equipment Services, Inc., Term Loan  9.710 %  8/17/10  B3  B  4,046,281 
  2,000  Williams Scotsman, Inc., Term Loan B  6.661 %  6/28/10  B2  BB  2,026,250 
            14,512,125 

  Construction & Engineering - 0.8% (0.5% of total investments)           
2,000  Maxim Crane Works, Term Loan C  9.625 %  1/28/12  N/R  N/R  2,050,000 

  Containers & Packaging - 5.4% (3.4% of total investments)           
4,963  Graham Packaging Company, L.P., Term Loan B  6.555 %  10/07/11  B2  B  5,030,737 
4,000  Graham Packaging Company, L.P., Term Loan C  8.250 %  3/15/12  B2  CCC+  4,080,000 
437  Smurfit-Stone Container Corporation, Deposit-Funded Commitment  2.100 %  11/01/11  Ba3  BB-  442,245 
1,999  Smurfit-Stone Container Corporation, Term Loan B  5.722 %  11/01/11  Ba3  BB-  2,024,741 
540  Smurfit-Stone Container Corporation, Term Loan C  5.875 %  11/01/11  Ba3  BB-  546,625 
1,466  United States Can Company, Term Loan B  7.650 %  1/15/10  B3  B  1,473,667 

            13,598,015 

  Diversified Telecommunication Services - 4.4% (2.7% of total investments)           
3,000  Fairpoint Communications, Inc., Term Loan  5.813 %  2/15/12  B1  BB-  3,034,125 
1,985  Intelsat, Ltd., Term Loan B  5.813 %  7/06/11  B1  B  2,005,678 
800  Qwest Corporation, Term Loan A  8.530 %  6/30/07  Ba3  BB  826,166 
5,000  Qwest Corporation, Term Loan B  6.950 %  6/30/10  Ba3  BB  5,010,938 
5,000  WCI Capital Corp., Term Loan B (a)(b)  0.000 %  9/30/07  N/R  N/R  75,000 

            10,951,907 

  Electric Utilities - 1.4% (0.9% of total investments)           
1,402  Allegheny Energy Supply Company, LLC, Term Loan C  5.788 %  3/08/11  Ba2  BB  1,418,569 
1,975  Calpine Construction Finance Company, L.P., Term Loan B  9.860 %  8/31/09  N/R  B  2,087,088 

            3,505,657 

  Electrical Equipment - 2.0% (1.2% of total investments)           
3,000  Mueller Group, Inc., Term Loan  6.401 %  10/02/12  B2  B+  3,043,661 
1,626  Sensus Metering Systems Inc., Term Loan B-1  5.955 %  12/17/10  B2  B+  1,645,397 
254  Sensus Metering Systems Inc., Term Loan B-2  5.970 %  12/17/10  B2  B+  256,708 

            4,945,766 

  Food Products - 2.4% (1.5% of total investments)           
5,000  Dole Holding Company, LLC, Term Loan  9.438 %  7/22/10  B3  BB  5,156,250 
913  Michael Foods, Inc., Term Loan B  5.187 %  11/20/10  B1  B+  928,154 

            6,084,404 

  Healthcare Equipment & Supplies - 0.7% (0.5% of total investments)           
1,849  Kinetic Concepts, Inc., Term Loan B-2  5.780 %  8/11/10  Ba3  BB  1,871,565 

  Healthcare Providers & Services - 9.0% (5.6% of total investments)           
5,376  Community Health Systems, Inc., Term Loan  5.610 %  8/19/11  N/R  BB-  5,450,175 
5,000  Davita Inc., Term Loan B  6.379 %  7/01/12  B1  BB-  5,079,860 
1,975  IASIS Healthcare LLC, Term Loan B  6.304 %  6/22/11  B1  B+  2,004,420 
2,154  Psychiatric Solutions, Term Loan B  5.730 %  6/30/12  B1  B+  2,179,423 
2,985  Select Medical Corporation, Term Loan  5.571 %  2/24/12  B1  BB-  2,990,389 
4,970  Vanguard Health Holding Company I, LLC, Term Loan  6.211 %  9/23/11  B2  B  5,041,444 

            22,745,711 

  Hotels, Restaurants & Leisure - 17.6% (11.1% of total investments)           
5,000  24 Hour Fitness Worldwide, Inc., Term Loan B  6.780 %  6/08/12  B2  B  5,084,375 
601  Ameristar Casinos, Inc., Incremental Term Loan  6.063 %  12/20/06  Ba3  BB+  604,647 
1,768  Ameristar Casinos, Inc., Term Loan B-1  6.063 %  12/20/06  Ba3  BB+  1,779,137 
4,988  Burger King Corporation, Term Loan B  5.830 %  7/17/12  Ba2  B+  5,045,392 
3,990  CCM Merger, Inc., Term Loan B  5.933 %  7/26/12  B1  B+  4,028,653 
1,985  Isle of Capri Casinos, Inc., Term Loan  5.845 %  4/26/08  Ba2  BB-  2,008,262 
4,406  Jack in the Box Inc., Term Loan  5.569 %  1/09/10  Ba2  BB  4,449,050 
7,990  OpBiz, LLC, Term Loan A  5.305 %  8/31/10  B3  B-  7,993,020 
20  OpBiz, LLC, Term Loan B (PIK)  8.055 %  8/31/10  B3  B-  19,899 
4,000  Penn National Gaming Inc., Term Loan B  6.082 %  5/26/12  Ba3  BB-  4,055,002 
2,772  Pinnacle Entertainment, Delayed Draw Term Loan  7.044 %  12/17/08  B1  BB-  2,807,098 
2,210  Pinnacle Entertainment, Term Loan B  7.090 %  8/27/10  B1  BB-  2,234,863 
1,959  Resorts International, Term Loan B  10.270 %  3/03/12  B2  B  1,962,089 
427  Venetian Casino Resort, LLC, Delayed Draw Term Loan  5.770 %  6/15/11  B1  BB-  431,390 
2,073  Venetian Casino Resort, LLC, Term Loan  5.770 %  6/15/11  B1  BB-  2,092,243 

            44,595,120 

  Household Durables - 3.3% (2.1% of total investments)           
3,674  Sealy Mattress Company, Term Loan D  5.731 %  4/06/12  B1  B+  3,712,038 
4,500  Shea Homes, Term Loan (c)  TBD   TBD  N/R  N/R  4,547,813 

            8,259,851 

  Household Products - 0.8% (0.5% of total investments)           
1,970  Prestige Brands, Inc., Term Loan B  6.316 %  4/06/11  B1  B+  1,997,087 

  Independent Power Producers & Energy Traders - 0.4% (0.2% of total investments)           
553  Covanta Energy Corporation, Letter of Credit  3.863 %  1/22/07  B1  B+  560,793 
446  Covanta Energy Corporation, Term Loan B  6.961 %  5/23/12  B1  B+  452,448 

            1,013,241 

  Insurance - 2.3% (1.4% of total investments)           
5,586  Conseco, Inc., Term Loan  5.970 %  6/22/10  B2  BB-  5,659,316 

  IT Services - 3.8% (2.4% of total investments)           
4,413  Fidelity National, Term Loan B  5.685 %  3/09/13  Ba3  BB  4,432,791 
4,988  SunGard Data Systems Inc., Term Loan B  6.280 %  1/25/13  B1  B+  5,037,091 

            9,469,882 

  Leisure Equipment & Products - 0.4% (0.2% of total investments)           
1,000  Mega Bloks, Term Loan B  5.885 %  9/30/10  Ba3  BB-  1,013,438 

  Machinery - 1.2% (0.7% of total investments)           
1,099  Dresser-Rand Group Inc., Term Loan  6.047 %  10/10/10  B1  B+  1,117,937 
1,830  Rexnord Corporation, Replacement Term Loan  6.151 %  12/31/11  B1  B+  1,854,040 

            2,971,977 

  Media - 24.3% (15.2% of total investments)           
6,209  American Media Operations, Inc., Term Loan C  6.813 %  4/01/07  B1  B  6,284,290 
6,000  Century Cable Holdings, LLC, Discretionary Term Loan (b)  8.750 %  12/31/09  N/R  N/R  5,948,250 
1,640  Century Cable Holdings, LLC, Revolver (b)(e)  7.750 %  10/25/10  N/R  N/R  1,613,350 
2,000  Century Cable Holdings, LLC, Revolver (b)(e)  7.750 %  10/25/10  N/R  N/R  1,967,500 
4,931  Charter Communications Operating, LLC, Term Loan B  7.500 %  4/07/11  B2  B  4,950,066 
2,294  Dex Media East, LLC, Term Loan B  5.781 %  11/10/08  Ba2  BB  2,307,118 
4,420  Dex Media West, LLC, Term Loan B  5.734 %  3/09/10  Ba2  BB  4,446,871 
1,985  Emmis Operating Company, Term Loan  5.720 %  11/10/11  Ba2  B+  2,001,252 
1,044  Gray Television, Inc., Term Loan B  5.350 %  12/31/10  Ba2  BB-  1,049,860 
5,000  Metro-Goldwyn-Mayer Studios, Inc., Term Loan B  6.270 %  4/12/12  N/R  N/R  5,048,438 
6,000  PRIMEDIA Inc., Term Loan  6.114 %  9/30/13  N/R  B  5,881,875 
4,337  R.H. Donnelley Inc., Tranche D  5.696 %  6/30/11  Ba3  BB  4,371,351 
2,985  Rainbow Media Holdings LLC, Term Loan  6.438 %  3/31/12  B1  BB+  3,015,783 
4,656  Regal Cinemas Corporation, Term Loan  6.020 %  11/10/10  Ba3  BB-  4,709,961 
1,728  Sun Media Corporation, Term Loan B  6.243 %  2/07/09  Ba2  BB  1,747,044 
3,000  UPC Financing Partnership, Term Loan H2  6.804 %  9/30/12  B1  B  3,029,219 
2,953  WMG Acquisition Corp., Term Loan  5.847 %  2/27/11  B1  B+  2,986,093 

            61,358,321 

  Metals & Mining - 2.0% (1.2% of total investments)           
4,951  Amsted Industries Incorporated, Term Loan B  6.623 %  10/15/10  B1  BB-  5,020,689 

  Multi-Utilities - 1.6% (1.0% of total investments)           
875  NRG Energy, Inc., Credit-Linked Deposit  3.920 %  12/24/11  Ba3  BB  881,198 
1,117  NRG Energy, Inc., Term Loan  5.895 %  12/20/11  Ba3  BB  1,124,471 
1,985  Reliant Energy, Inc., Term Loan  6.112 %  4/30/10  B1  B+  1,993,684 

            3,999,353 

  Oil, Gas & Consumable Fuels - 2.0% (1.2% of total investments)           
800  Coffeyville Resources LLC, Letter of Credit  6.563 %  6/24/12  B1  BB-  814,000 
1,197  Coffeyville Resources LLC, Term Loan B  6.566 %  6/24/12  B1  BB-  1,217,948 
1,125  El Paso Corporation, Deposit-Funded Commitment  3.764 %  11/23/09  B3  B  1,133,359 
1,845  El Paso Corporation, Term Loan  6.813 %  11/23/09  B3  B  1,861,016 

            5,026,323 

  Paper & Forest Products - 1.7% (1.1% of total investments)           
1,195  Boise Cascade Holdings, LLC, Term Loan D  5.790 %  3/29/11  Ba3  BB  1,213,123 
2,993  NewPage Corporation, Term Loan B  6.788 %  5/22/11  B1  B  3,022,425 

            4,235,548 

  Pharmaceuticals - 0.8% (0.5% of total investments)           
1,990  Talecris Biotherapeutics Inc., Term Loan B  7.090 %  3/31/10  N/R  N/R  1,994,975 

  Real Estate - 6.3% (3.9% of total investments)           
1,781  General Growth Properties, Inc., Term Loan A  5.610 %  10/28/04  Ba2  BB+  1,790,334 
4,968  General Growth Properties, Inc., Term Loan B  6.090 %  11/12/08  Ba2  BB+  5,028,605 
937  Lion Gables, Term Loan  5.630 %  9/30/06  N/R  BB+  942,407 
4,900  LNR Property Corp., Term Loan  6.731 %  2/03/08  B2  B+  4,939,661 
3,000  LNR Property Corp., Mezzanine Term Loan B  8.977 %  2/03/08  B2  B+  3,015,938 

            15,716,945 

  Specialty Retail - 4.5% (2.8% of total investments)           
1,363  Micro Warehouse, Inc., Term Loan B (a)(b)  0.000 %  1/30/07  N/R  N/R  40,889 
2,993  Movie Gallery Inc., Term Loan B  7.830 %  4/01/11  B2  B  2,932,961 
4,060  Norwood Promotional Products, Inc., Term Loan A  10.125 %  8/16/09  N/R  N/R  4,120,531 
5,362  Norwood Promotional Products, Inc., Term Loan B  1.000 %  8/16/11  N/R  N/R  2,077,921 
2,000  TravelCenters of America Inc., Term Loan  5.710 %  6/30/11  B1  BB  2,023,750 

            11,196,052 

  Textiles, Apparel & Luxury Goods - 3.6% (2.3% of total investments)           
5,225  Jostens IH Corp., Term Loan C  5.943 %  7/29/10  B1  B+  5,312,357 
3,750  William Carter Company, Term Loan B  5.718 %  7/17/12  B1  BB  3,800,391 

            9,112,748 

  Trading Companies & Distributors - 0.8% (0.5% of total investments)           
2,000  Ashtead Group Public Limited Company, Term Loan  6.063 %  11/12/09  N/R  BB  2,021,663 

  Total Variable Rate Senior Loan Interests (cost $349,113,423)          342,259,775 

Principal 
Amount  
(000)
 
    Stated 
   Maturity 
   
Ratings**
     
Description(1)  Coupon   Moody's  S&P  Value 

  CORPORATE BONDS - 16.3% (10.2% of total investments)           
  Hotels, Restaurants & Leisure - 7.2% (4.6% of total investments)           
$ 5,350  Mandalay Resort Group  6.450 %  2/01/06  Ba2  BB+  5,390,125 
1,500  MGM Grand  7.250 %  10/15/06  Ba1  BB+  1,526,250 
7,000  MGM Mirage  9.750 %  6/01/07  Ba2  BB-  7,385,000 
1,443  Park Place Entertainment  7.875 %  12/15/05  Ba2  BB-  1,450,215 
2,400  Park Place Entertainment  8.875 %  9/15/08  Ba2  BB-  2,586,000 

            18,337,590 

  Household Durables - 1.2% (0.7% of total investments)           
3,000  Standard Pacific Corporation  6.500 %  10/01/08  Ba2  BB  2,955,000 

  Machinery - 0.8% (0.5% of total investments)           
2,000  Navistar International, Series B  9.375 %  6/01/06  Ba3  BB-  2,045,000

  Media - 4.4% (2.7% of total investments)         
1,930  AMC Entertainment  9.875 %  2/01/12  B3  CCC+  1,852,800
2,000  Cablevision Systems Corp. Floating Rate Note, 4.500% plus six-month LIBOR  8.966 %  4/01/09  B3  B+  2,055,000
4,500  Emmis Operating Company, Floating Rate Note, 5.875% plus three-month LIBOR, 144A  10.135 %  6/15/12  B3  B-  4,533,750
2,500  PRIMEDIA Inc., Floating Rate Note, 5.375% plus three-month LIBOR  9.635 %  5/15/10  B3  B  2,518,750

            10,960,300

  Oil, Gas & Consumable Fuels - 2.7% (1.7% of total investments)         
6,417  Tesoro Petroleum Corporation  8.000 %  4/15/08  Ba2  BBB-  6,705,765

  Total Corporate Bonds (cost $41,615,512)          41,003,655

Shares (000)  Description(1)          Value

  EQUITIES - 0.0% (0.0% of total investments)         
  Auto Components - 0.0% (0.0% of total investments)         
280  MetalForming Technologies, Inc. (b) (f)         

  Total Equities (cost $0)         

  WARRANTS - 0.0% (0.0% of total investments)         
  Multi-Utilities - 0.0% (0.0% of total investments)         
6  Reliant Energy, Inc.          46,284

  Total Warrants (cost $40,254)          46,284

Principal 
Amount   (000) 
         
Description(1)          Value

  REPURCHASE AGREEMENTS - 7.8% (4.8% total investments)         
  State Street Bank, 3.730%, dated 10/31/05, due 11/01/05, repurchase price $19,506,655         
$ 19,505   collateralized by $15,965,000 U.S. Treasury Bonds, 7.250%, due 5/15/16, value $19,896,605          19,504,634


  Total Repurchase Agreements (cost $19,504,634)          19,504,634

  Total Investments (cost $410,273,823) - 160.2%          402,814,348

  Borrowings Payable - (41.0)%†          (103,000,000)

  Other Assets Less Liabilities - (0.9)%          (2,431,285)

  Preferred Shares, at Liquidation Value (18.3)%          (46,000,000)

  Net Assets Applicable to Common Shares - 100%          $ 251,383,063





(1 )  All percentages shown in the Portfolio of Investments are based on net assets applicable to Common shares 
  unless otherwise noted. 
(2 )  Senior Loans in which the Fund invests generally pay interest at rates which are periodically adjusted by 
  reference to a base short-term, floating lending rate plus an assigned fixed rate. These floating lending rates 
  are generally (i) the lending rate referenced by the London Inter-Bank Offered Rate ("LIBOR"), or (ii) the 
  prime rate offered by one or more major United States banks. 
  The Fund did not have any unfunded loan commitments at October 31, 2005. 
  Senior Loans may be considered restricted in that the Fund ordinarily is contractually obligated to receive 
  approval from the Agent Bank and/or Borrower prior to the disposition of a Senior Loan. 
*   Senior Loans in the Fund’s portfolio generally are subject to mandatory and/or optional prepayment. Because 
  of these mandatory prepayment conditions and because there may be significant economic incentives for a 
  Borrower to prepay, prepayments of Senior Loans in the Fund’s portfolio may occur. As a result, the actual 
  remaining maturity of Senior Loans held in the Fund’s portfolio may be substantially less than the stated 
  maturities shown. 
**   Ratings below Baa by Moody’s Investor Service, Inc. or BBB by Standard & Poor’s Group are considered to 
  be below investment grade. 
(a)   At or subsequent to October 31, 2005, this issue was non-income producing. 
(b)   At or subsequent to October 31, 2005, this issue was under the protection of the Federal Bankruptcy Court. 
(c)   Investment purchased on a when-issued or delayed delivery basis. 
(d)   Portion of investment purchased on a when-issued or delayed delivery basis. 
(e)   Position represents a participation commitment outstanding at October 31, 2005. The Fund had 
  the following participation commitments outstanding at October 31, 2005: 

Commitment      
Counterparty  Amount  Value 

Morgan Stanley  $ 1,640,000  $ 1,613,350 
Bear, Stearns & Co., Inc.  2,000,000  1,967,500 


(f)   Investment valued at fair value using methods determined in good faith by, or at the discretion of, the Board 
  of Trustees. 
144 A  Securities are exempt from registration under Rule 144A of the Securities Act of 1933, as amended. These 
  securities may only be resold in transactions exempt from registration which are normally those transactions 
  with qualified institutional buyers. 
TBD   Senior Loan purchased on a when-issued or delayed delivery basis. Certain details associated with this 
  purchase are not known prior to the settlement date of the transaction. In addition, Senior Loans typically 
  trade without accrued interest and therefore a weighted average coupon rate is not available prior to settlement. 
  At settlement, if still unknown, the borrower or counterparty will provide the Fund with the final weighted 
  average coupon rate and maturity date. 
(PIK)   In lieu of cash payment, interest accrued on “Payment in Kind” investment increases principal outstanding. 
N/R   Investment is not rated. 
  Borrowings payable as a percentage of total investments is (25.6%). 

Income Tax Information

The following information is presented on an income tax basis. Differences between amounts for financial statement and federal income tax purposes are primarily due to timing differences in recognizing certain gains and losses on investment transactions.

At October 31, 2005, the cost of investments was $410,273,823.

Gross unrealized appreciation and gross unrealized depreciation of investments at October 31, 2005, were as follows:






Gross unrealized:   
     Appreciation  $ 4,919,445  
     Depreciation  (12,378,920 ) 

Net unrealized appreciation (depreciation) of investments  $ (7,459,475 ) 






Item 2. Controls and Procedures.

  1. The registrant's principal executive and principal financial officers, or persons performing similar functions, have concluded that the registrant's disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940, as amended (the "1940 Act") (17 CFR 270.30a-3(c))) are effective, as of a date within 90 days of the filing date of this report that includes the disclosure required by this paragraph, based on their evaluation of the controls and procedures required by Rule 30a-3(b) under the 1940 Act (17 CFR 270.30a-3(b)) and Rule 13a-15(b) or 15d-15(b) under the Securities Exchange Act of 1934 (17 CFR 240.13a-15(b) or 240.15d-15(b)).
  2. There were no changes in the registrant's internal control over financial reporting (as defined in Rule 30a-3(d) under the 1940 Act (17 CFR 270.30a-3(d)) that occurred during the registrant's last fiscal quarter that have materially affected, or are reasonably likely to materially affect, the registrant's internal control over financial reporting.

Item 3. Exhibits.

File as exhibits as part of this Form a separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2(a) under the 1940 Act (17 CFR 270.30a-2(a)), exactly as set forth below: EX-99 CERT Attached hereto.


SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

(Registrant)         Nuveen Senior Income Fund        

By (Signature and Title)*          /s/ Jessica R. Droeger                     
                                                    Jessica R. Droeger
                                                    Vice President and Secretary

Date         12/29/05        

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By (Signature and Title)*         /s/ Gifford R. Zimmerman                    
                                                   Gifford R. Zimmerman
                                                   Chief Administrative Officer (principal executive officer) 

Date         12/29/05        

By (Signature and Title)*         /s/ Stephen D. Foy                              
                                                   Stephen D. Foy
                                                   Vice President and Controller (principal financial officer) 

Date         12/29/05        

* Print the name and title of each signing officer under his or her signature.