1
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                   SCHEDULE TO

        TENDER OFFER STATEMENT UNDER SECTION 14(d)(1) OR 13(e)(1) OF THE
                         SECURITIES EXCHANGE ACT OF 1934
                                (AMENDMENT NO. 3)

                                       AND
                                  SCHEDULE 13D
                    UNDER THE SECURITIES EXCHANGE ACT OF 1934
                               (AMENDMENT NO. 20)


                           Century Properties Fund XV
                           --------------------------
                       (Name of Subject Company (Issuer))

                        AIMCO Properties, L.P. -- Offeror
                        ---------------------------------
            (Names of Filing Persons (Identifying Status as Offeror,
                            Issuer or Other Person))

                            Limited Partnership Units
                            -------------------------
                           (Title of Class Securities)

                                      None
                                      ----
                       (CUSIP Number of Class Securities)

                                 Patrick J. Foye
                   Apartment Investment And Management Company
                           Colorado Center, Tower Two
                   2000 South Colorado Boulevard, Suite 2-1000
                             Denver, Colorado 80222
                                 (303) 757-8101

           (Name, address, and telephone numbers of person authorized
       to receive notices and communications on behalf of filing persons)

                                    Copy To:

                              Jonathan L. Friedman
                    Skadden, Arps, Slate, Meagher & Flom LLP
                       300 South Grand Avenue, 34th Floor
                          Los Angeles, California 90071
                                 (213) 687-5000


   2


                            Calculation of Filing Fee




Transaction valuation*                                     Amount of filing fee
- ----------------------                                     --------------------
                                                        
$5,360,455.90                                              $1,072.09


*        For purposes of calculating the fee only. This amount assumes the
         purchase of 35,035.66 units of limited partnership interest of the
         subject partnership for $153 per unit. The amount of the filing fee,
         calculated in accordance with Section 14(g)(1)(B)(3) and Rule 0-11(d)
         under the Securities Exchange Act of 1934, as amended, equals 1/50th of
         one percent of the aggregate of the cash offered by the bidder.

[X]      Check the box if any part of the fee is offset as provided by Rule
         0-11(a)(2) and identify the filing with which the offsetting fee was
         previously paid. Identify the previous filing by registration
         statement number, or the Form or Schedule and the date of its filing.

Amount Previously Paid:  $1,072.09         Filing Party: AIMCO Properties, L.P.

Form or Registration No.: Schedule TO      Date Filed: August 4, 2000

                                   ----------

[ ] Check the box if the filing relates solely to preliminary communications
made before the commencement of a tender offer.

Check the appropriate boxes below to designate any transactions to which the
statement relates:

[X] third-party tender offer subject to Rule 14d-1

[ ] issuer tender offer subject to Rule 13e-4

[ ] going-private transaction subject to Rule 13e-3

[X] amendment to Schedule 13D under Rule 13d-2

Check the following box if the filing is a final amendment reporting the results
of the tender offer: [ ]


                                        2

   3



CUSIP No.   NONE

1.       NAME OF REPORTING PERSONS
         S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only)

                  AIMCO PROPERTIES, L.P.
                  84-1275721

2.       CHECK THE APPROPRIATE BOX IF A MEMBER OF GROUP
                                                                         (a) [ ]
                                                                         (b) [X]
3.       SEC USE ONLY

4.       SOURCE OF FUNDS

                  WC, BK

5.       (CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
         ITEMS 2(d) OR 2(e))                                                 [ ]

6.       CITIZENSHIP OR PLACE OF ORGANIZATION

                  Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON

7.       SOLE VOTING POWER

                  --

8.       SHARED VOTING POWER

                  15,142.17 Units

9.       SOLE DISPOSITIVE POWER

                  --

10.      SHARED DISPOSITIVE POWER

                  15,142.17 Units

11.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                  15,142.17 Units

12.      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
                                                                             [ ]

13.      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                  Approximately 16.49%

14.      TYPE OF REPORTING PERSON

                  PN


                                        3

   4



CUSIP No.   NONE

1.       NAME OF REPORTING PERSONS
         S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only)

                  AIMCO-GP, INC.

2.       CHECK THE APPROPRIATE BOX IF A MEMBER OF GROUP
                                                                         (a) [ ]
                                                                         (b) [X]

3.       SEC USE ONLY

4.       SOURCE OF FUNDS

                  Not Applicable

5.       (CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
         ITEMS 2(d) OR 2(e))                                                 [ ]

6.       CITIZENSHIP OR PLACE OF ORGANIZATION

                  Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON

7.       SOLE VOTING POWER

                  --

8.       SHARED VOTING POWER

                  15,142.17 Units

9.       SOLE DISPOSITIVE POWER

                  --

10.      SHARED DISPOSITIVE POWER

                  15,142.17 Units

11.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                  15,142.17 Units

12.      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
                                                                             [ ]

13.      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                  Approximately 16.49%

14.      TYPE OF REPORTING PERSON

                  CO


                                        4

   5



CUSIP No.   NONE

1.       NAME OF REPORTING PERSONS
         S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only)

                  APARTMENT INVESTMENT AND MANAGEMENT COMPANY
                  84-129577

2.       CHECK THE APPROPRIATE BOX IF A MEMBER OF GROUP
                                                                         (a) [ ]
                                                                         (b) [X]

3.       SEC USE ONLY

4.       SOURCE OF FUNDS

                  Not Applicable

5.       (CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
         ITEMS 2(d) OR 2(e))                                                 [ ]

6.       CITIZENSHIP OR PLACE OF ORGANIZATION

                  Maryland

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON

7.       SOLE VOTING POWER

                  --

8.       SHARED VOTING POWER

                  54,944.34 Units

9.       SOLE DISPOSITIVE POWER

                  --

10.      SHARED DISPOSITIVE POWER

                  54,944.34 Units

11.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                  54,944.34 Units

12.      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
                                                                             [ ]

13.      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                  Approximately 59.84%

14.      TYPE OF REPORTING PERSON

                  CO


                                        5

   6



CUSIP No.   NONE

1.       NAME OF REPORTING PERSONS
         S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only)

                  INSIGNIA PROPERTIES, L.P.

2.       CHECK THE APPROPRIATE BOX IF A MEMBER OF GROUP
                                                                         (a) [ ]
                                                                         (b) [X]

3.       SEC USE ONLY

4.       SOURCE OF FUNDS

                  Not Applicable

5.       (CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
         ITEMS 2(d) OR 2(e))                                                 [ ]

6.       CITIZENSHIP OR PLACE OF ORGANIZATION

                  Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON

7.       SOLE VOTING POWER

                  --

8.       SHARED VOTING POWER

                  39,802.17 Units

9.       SOLE DISPOSITIVE POWER

                  --

10.      SHARED DISPOSITIVE POWER

                  39,802.17 Units

11.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                  39,802.17 Units

12.      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
                                                                             [ ]

13.      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                    Approximately 43.35%

14.      TYPE OF REPORTING PERSON

                  PN


                                        6

   7



CUSIP No.   NONE

1.       NAME OF REPORTING PERSONS
         S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only)

                  AIMCO/IPT, INC.

2.       CHECK THE APPROPRIATE BOX IF A MEMBER OF GROUP
                                                                         (a) [ ]
                                                                         (b) [X]

3.       SEC USE ONLY

4.       SOURCE OF FUNDS

                  Not Applicable

5.       (CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
         ITEMS 2(d) OR 2(e))                                                 [ ]

6.       CITIZENSHIP OR PLACE OF ORGANIZATION

                  Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON

7.       SOLE VOTING POWER

                  --

8.       SHARED VOTING POWER

                  39,802.17 Units

9.       SOLE DISPOSITIVE POWER

                  --

10.      SHARED DISPOSITIVE POWER

                  39,802.17 Units

11.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                  39,802.17 Units

12.      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
                                                                             [ ]

13.      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                     Approximately 43.35%

14.      TYPE OF REPORTING PERSON

                  CO



                                        7

   8



CUSIP No.   NONE

1.       NAME OF REPORTING PERSONS
         S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only)

                  MADISON RIVER PROPERTIES, L.L.C.

2.       CHECK THE APPROPRIATE BOX IF A MEMBER OF GROUP
                                                                         (a) [ ]
                                                                         (b) [X]

3.       SEC USE ONLY

4.       SOURCE OF FUNDS

                  Not Applicable

5.       (CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
         ITEMS 2(d) OR 2(e))                                                 [ ]

6.       CITIZENSHIP OR PLACE OF ORGANIZATION

                  Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON

7.       SOLE VOTING POWER

                  --

8.       SHARED VOTING POWER

                  4,222 Units

9.       SOLE DISPOSITIVE POWER

                  --

10.      SHARED DISPOSITIVE POWER

                  4,222 Units

11.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                  4,222 Units

12.      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
                                                                             [ ]

13.      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                    Approximately 4.6%

14.      TYPE OF REPORTING PERSON

                  OO


                                        8

   9



                   AMENDMENT NO. 3 TO TENDER OFFER STATEMENT/
                        AMENDMENT NO. 20 TO SCHEDULE 13D

         This Statement (the "Statement") constitutes (a) Amendment No.3 to the
Tender Offer Statement on Schedule TO of AIMCO Properties, L.P. (the "AIMCO
OP"), relating to an offer to purchase units of limited partnership interest
("Units") of Century Properties Fund XV (the "Partnership"); and (b) Amendment
No. 20 to the Schedule 13D (the "Schedule 13D") originally filed with the
Securities and Exchange Commission (the "Commission") on August 28, 1995, by
Insignia Financial Group, Inc. "(Insignia"), Insignia NPI, L.L.C. ("NPI"),
Riverside Drive, L.L.C. ("Riverside") and Andrew L. Farkas, as amended by (i)
Amendment No. 1, filed with the Commission on January 30, 1996, by Insignia,
IFGP Corporation ("IFGP"), NPI, Riverside, Insignia Commercial Group, Inc.
("Commercial"), Insignia Properties Corporation ("IPC") and Andrew L. Farkas,
(ii) Amendment No. 2, filed with the Commission on February 27, 1996, by
Insignia, IFGP, NPI, Riverside, Commercial, IPC and Andrew L. Farkas, (iii)
Amendment No. 3 filed with the Commission on January 16, 1997, by Insignia,
Insignia Properties, L.P. ("IPLP"), Commercial, Insignia Properties Trust
("IPT") and Andrew L. Farkas, (iv) Amendment No. 4, filed with the Commission on
December 17, 1997, by Madison River Properties, L.L.C. ("Madison River"), IPLP,
IPT, Insignia and Andrew L. Farkas, (v) Amendment No. 5, filed with the
Commission on December 18, 1997, by Madison River, IPLP, IPT, Insignia and
Andrew L. Farkas, (vi) Amendment No. 6, filed with the Commission on January 15,
1998, by Madison River, IPLP, IPT, Insignia and Andrew L. Farkas, (vii)
Amendment No. 7, filed with the Commission on January 27, 1998, by Madison
River, IPLP, IPT, Insignia and Andrew L. Farkas, (viii) Amendment No. 8, filed
with the Commission on February 2, 1998, by Madison River, IPLP, IPT, Insignia
and Andrew L. Farkas, (ix) Amendment No. 9, filed with the Commission on March
12, 1998, by Madison River, IPLP, IPT, Insignia and Andrew L. Farkas, (x)
Amendment No. 10, filed with the Commission on November 6, 1998, by Madison
River, IPLP, IPT, AIMCO OP, AIMCO-GP, Inc. ("AIMCO-GP") and Apartment Investment
and Management Company ("AIMCO"), (xi) Amendment No. 11, filed with the
Commission on June 10, 1999, by Madison River, AIMCO/IPT, Inc. ("AIMCO/IPT"),
IPLP, AIMCO OP, AIMCO-GP and AIMCO, (xii) Amendment No. 12, filed with the
Commission on July 8, 1999, by Madison River, AIMCO/IPT, IPLP, AIMCO OP,
AIMCO-GP and AIMCO, (xiii) Amendment No. 13, filed with the Commission on July
30, 1999, by Madison River, AIMCO/IPT, IPLP, AIMCO OP, AIMCO-GP, and AIMCO,
(xiv) Amendment No. 14, filed with the Commission on November 17, 1999, by
Madison River, AIMCO/IPT, IPLP, AIMCO OP, AIMCO-GP and AIMCO, (xv) Amendment No.
15, dated December 16, 1999, by Madison River, AIMCO/IPT, IPLP, AIMCO OP,
AIMCO-GP and AIMCO, (xvi) Amendment No. 16, dated January 10, 2000, by Madison
River, AIMCO/IPT, IPLP, AIMCO OP, AIMCO-GP and AIMCO, and (xvii) Amendment No.
17, dated August 2, 2000, by Madison River, AIMCO/IPT, IPLP, AIMCO OP, AIMCO-GP
and AIMCO, (xviii) Amendment No. 18, dated August 22, 2000, by Madison River,
AIMCO/IPT, IPLP, AIMCO OP, AIMCO-GP and AIMCO, and (xix) Amendment No. 19, dated
September 1, 2000, by Madison River, AIMCO/IPT, IPLP, AIMCO OP, AIMCO-GP and
AIMCO.

                                   ----------

Item 12.  Exhibits.

         (a)(1)     Offer to Purchase, dated August 2, 2000. (Previously filed.)

         (a)(2)     Letter of Transmittal and related Instructions. (Previously
                    filed.)

         (a)(3)     Letter, dated August 2, 2000, from AIMCO OP to the limited
                    partners of the Partnership. (Previously filed.)

         (a)(4)     Reminder Letter, from AIMCO OP to the limited partners of
                    the Partnership. (Previously filed.)

         (a)(5)     Supplement to Offer to Purchase, dated September 5, 2000.
                    (Previously filed.)


                                        9

   10



         (a)(6)     Letter, dated August 30, 2000, from AIMCO OP to the limited
                    partners of the Partnership. (Previously filed.)

         (a)(7)     Press Release, dated September 5, 2000. (Previously filed.)

         (a)(8)     Letter, dated September 18, 2000, from AIMCO OP to the
                    limited partners of the Partnership.

         (a)(9)     Press Release, dated September 18, 2000.

         (b)(1)     Credit Agreement (Secured Revolving Credit Facility), dated
                    as of August 16, 1999, among AIMCO Properties, L.P., Bank of
                    America, Bank Boston, N.A., and First Union National Bank.
                    (Exhibit 10.1 to AIMCO's Current Report on Form 8-K, dated
                    August 16, 1999, is incorporated herein by this reference.)

         (b)(2)     Amended and Restated Credit Agreement, dated as of March 15,
                    2000, among AIMCO Properties, L.P., Bank of America, Bank
                    Boston, N.A., and First Union National Bank. (Exhibit 10.20
                    to AIMCO Properties, L.P.'s Annual Report on Form 10-K for
                    the year ended December 31, 1999, is incorporated herein by
                    this reference.)

         (b)(3)     First Amendment to $345,000,000 Amended and Restated Credit
                    Agreement, dated as of April 14, 2000, among AIMCO
                    Properties, L.P., Bank of America, as Administrative Agent,
                    and U.S. Bank National Association, as Lender. (Exhibit 10.4
                    to AIMCO's Quarterly Report on Form 10-Q for the quarter
                    ended March 31, 2000, is incorporated herein by this
                    reference.)

         (d)        Not applicable.

         (g)        Not applicable.

         (h)        Not applicable.

         (z)(1)     Agreement of Joint Filing, dated November 15, 1999, among
                    AIMCO, AIMCO-GP, AIMCO OP, AIMCO/IPT, IPLP and Madison
                    River. (Previously filed.)


                                       10

   11



                                    SIGNATURE

         After due inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.


Date: September 18, 2000
                                         AIMCO PROPERTIES, L.P.

                                         By: AIMCO-GP, INC.
                                                 (General Partner)

                                         By: /s/ Patrick J. Foye
                                             -----------------------------------
                                             Executive Vice President

                                         AIMCO/IPT, INC.

                                         By: /s/ Patrick J. Foye
                                             -----------------------------------
                                             Executive Vice President

                                         INSIGNIA PROPERTIES, L.P.

                                         By: AIMCO/IPT, INC.
                                               (General Partner)

                                         By: /s/ Patrick J. Foye
                                             -----------------------------------
                                             Executive Vice President

                                         MADISON RIVER PROPERTIES, L.L.C.

                                         By: /s/ Patrick J. Foye
                                             -----------------------------------
                                             Executive Vice President

                                         AIMCO-GP, INC.

                                         By: /s/ Patrick J. Foye
                                             -----------------------------------
                                             Executive Vice President

                                         APARTMENT INVESTMENT
                                         AND MANAGEMENT COMPANY

                                         By: /s/ Patrick J. Foye
                                             -----------------------------------
                                             Executive Vice President




   12


                                INDEX TO EXHIBITS




        EXHIBIT
        NUMBER                             DESCRIPTION
        -------                            -----------
                 
         (a)(1)     Offer to Purchase, dated August 2, 2000. (Previously filed.)

         (a)(2)     Letter of Transmittal and related Instructions. (Previously
                    filed.)

         (a)(3)     Letter, dated August 2, 2000, from AIMCO OP to the limited
                    partners of the Partnership. (Previously filed.)

         (a)(4)     Reminder Letter, from AIMCO OP to the limited partners of
                    the Partnership. (Previously filed.)

         (a)(5)     Supplement to Offer to Purchase, dated September 5, 2000.
                    (Previously filed.)

         (a)(6)     Letter, dated August 30, 2000, from AIMCO OP to the limited
                    partners of the Partnership. (Previously filed.)

         (a)(7)     Press Release, dated September 5, 2000. (Previously filed.)

         (a)(8)     Letter, dated September 18, 2000, from AIMCO OP to the
                    limited partners of the Partnership.

         (a)(9)     Press Release, dated September 18, 2000.

         (b)(1)     Credit Agreement (Secured Revolving Credit Facility), dated
                    as of August 16, 1999, among AIMCO Properties, L.P., Bank of
                    America, Bank Boston, N.A., and First Union National Bank.
                    (Exhibit 10.1 to AIMCO's Current Report on Form 8-K, dated
                    August 16, 1999, is incorporated herein by this reference.)

         (b)(2)     Amended and Restated Credit Agreement, dated as of March 15,
                    2000, among AIMCO Properties, L.P., Bank of America, Bank
                    Boston, N.A., and First Union National Bank. (Exhibit 10.20
                    to AIMCO Properties, L.P.'s Annual Report on Form 10-K for
                    the year ended December 31, 1999, is incorporated herein by
                    this reference.)

         (b)(3)     First Amendment to $345,000,000 Amended and Restated Credit
                    Agreement, dated as of April 14, 2000, among AIMCO
                    Properties, L.P., Bank of America, as Administrative Agent,
                    and U.S. Bank National Association, as Lender. (Exhibit 10.4
                    to AIMCO's Quarterly Report on Form 10-Q for the quarter
                    ended March 31, 2000, is incorporated herein by this
                    reference.)

         (d)        Not applicable.

         (g)        Not applicable.

         (h)        Not applicable.

         (z)(1)     Agreement of Joint Filing, dated November 15, 1999, among
                    AIMCO, AIMCO- GP, AIMCO OP, AIMCO/IPT, IPLP and Madison
                    River. (Previously filed.)