SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                   ----------

                                   SCHEDULE TO
                                 (Rule 14d-100)
            TENDER OFFER STATEMENT UNDER SECTION 14(d)(1) OR 13(e)(1)
                     OF THE SECURITIES EXCHANGE ACT OF 1934


                          NATIONAL PROPERTY INVESTORS 6
                       (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 of Securities)

                                      NONE
                      (CUSIP Number of Class of Securities)

                                 Patrick J. Foye
                            Executive Vice President
                   Apartment Investment And Management Company
                           Colorado Center, Tower Two
                   2000 South Colorado Boulevard, Suite 2-1000
                             Denver, Colorado 80222
                                 (303) 757-8081
- --------------------------------------------------------------------------------
                 (Name, Address, and Telephone Numbers of Person
  Authorized to Receive Notices and Communications on Behalf of Filing Persons)

                                    Copy To:

                                Gregory M. Chait
                                  Robert Barker
                     Powell, Goldstein, Frazer & Murphy LLP
                   191 Peachtree Street, N.E., Sixteenth Floor
                             Atlanta, Georgia 30303
                                 (404) 572-6600

                            CALCULATION OF FILING FEE

<Table>
<Caption>

Transaction Valuation*                Amount of Filing Fee
- ----------------------                --------------------
                                   

$2,827,363                            $260.12
</Table>

    * For purposes of calculating the fee only. This amount assumes the purchase
of 38,731 units of limited partnership interest of National Property Investors 6
for $73.00 per unit. Pursuant to Rule 0-11 under the Exchange Act of 1934, the
filing fee equals $92 per $1,000,000 (prorated for amounts less than
$1,000,000). The filing fee is calculated by multiplying the aggregate offering
amount by .000092.

         [ ] 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:                  Filing Party:
                                 -------------                  -------------
         Form or Registration No.:                Date Filed:
                                   -----------                ---------------

         [ ] 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:

<Table>
                                                            
         [X] third-party tender offer subject to Rule 14d-1.    [ ] going-private transaction subject to Rule 13e-3.

         [ ] issuer tender offer subject to Rule 13e-4.         [ ] amendment to Schedule 13D under Rule 13d-2.
</Table>

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





                             TENDER OFFER STATEMENT

         This Tender Offer Statement on Schedule TO relates to the tender offer
by AIMCO Properties, L.P., a Delaware limited partnership, to purchase
outstanding units of limited partnership interest of National Property Investors
6, a California limited partnership, at a price of $73.00 per unit in cash,
subject to the conditions set forth in the Offer to Purchase, dated May 8, 2002,
and in the related Letter of Transmittal and Acknowledgment and Agreement,
which, as amended and supplemented from time to time, together constitute the
tender offer. Copies of the Offer to Purchase, Letter of Transmittal and
Acknowledgment and Agreement are filed with this Schedule TO as Exhibits 1, 2
and 3, respectively.

         The information in Exhibits 1-3, 5 and 6 is incorporated in this
Schedule TO by reference in answer to items 1 through 11 of Schedule TO.

         Neither AIMCO Properties, L.P. nor any of the people or entities listed
on Annex I to the Offer to Purchase has, during the last five years, been
convicted in a criminal proceeding (excluding traffic violations or similar
misdemeanors), or was, during the last five years, a party to any judicial or
administrative proceeding (except for matters that were dismissed without
sanction or settlement) that resulted in a judgment, decree or final order
enjoining the person from future violations of, or prohibiting activities
subject to, federal or state securities laws, or a finding of any violation of
federal or state securities laws.

================================================================================

Item 12.   Exhibits.

1        Offer to Purchase limited partnership units of National Property
         Investors 6, dated May 8, 2002.

2        Letter of Transmittal and related instructions, dated May 8, 2002
         (included as Annex II to the Offer to Purchase attached as Exhibit
         (1)(a)).

3        Acknowledgement and Agreement, dated May 8, 2002.

4        Letter, dated May 8, 2002, from AIMCO Properties, L.P., to the limited
         partners of National Property Investors 6.

5        Third Amended and Restated Credit Agreement (Secured Revolving Credit
         Facility), dated as of November 6, 2001, by and among AIMCO Properties,
         L.P., AIMCO/Bethesda Holdings, Inc., NHP Management Company, Bank of
         America, N.A., Fleet National Bank, and First Union National Bank.
         (Exhibit 10.1 to AIMCO Properties, L.P.'s Quarterly Report on Form 10-Q
         for the quarter ended September 30, 2001, filed on November 14, 2001,
         is incorporated herein by this reference).

6        Annual Report of AIMCO Properties, L.P. for the year ended December 31,
         2001 filed on Form 10-K405 on April 1, 2002, is incorporated herein by
         this reference.





                                    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:  May 8, 2002
                                          AIMCO PROPERTIES, L.P.

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

                                          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











                                  EXHIBIT INDEX


<Table>
<Caption>
EXHIBIT
NO.           DESCRIPTION
- -------       -----------
          

   1          Offer to Purchase limited partnership units of National Property
              Investors 6, dated May 8, 2002.

   2          Letter of Transmittal and related instructions, dated May 8, 2002
              (included as Annex II to the Offer to Purchase attached as Exhibit
              (1)(a)).

   3          Acknowledgement and Agreement, dated May 8, 2002.

   4          Letter, dated May 8, 2002, from AIMCO Properties, L.P., to the
              limited partners of National Property Investors 6.

   5          Third Amended and Restated Credit Agreement (Secured Revolving
              Credit Facility), dated as of November 6, 2001, by and among AIMCO
              Properties, L.P., AIMCO/Bethesda Holdings, Inc., NHP Management
              Company, Bank of America, N.A., Fleet National Bank, and First
              Union National Bank. (Exhibit 10.1 to AIMCO Properties, L.P.'s
              Quarterly Report on Form 10-Q for the quarter ended September 30,
              2001, filed on November 14, 2001, is incorporated herein by this
              reference).

   6          Annual Report of AIMCO Properties, L.P. for the year ended
              December 31, 2001 filed on Form 10-K405 on April 1, 2002, is
              incorporated herein by this reference.
</Table>