SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                 SCHEDULE TO/A
                               (AMENDMENT NO. 1)

   TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES
                              EXCHANGE ACT OF 1934

                          National Property Investors 4

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                       (Name of Subject Company (Issuer))

                             AIMCO Properties, L.P.
                   Apartment Investment and Management Company
                                 AIMCO-GP, Inc.
                          NPI Equity Investments, Inc.

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                      (Names of Filing Persons -- Offerors)

                            Limited Partnership Units

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                           (Title of Class Securities)

                                      None

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                       (CUSIP Number of Class Securities)

                                 Martha L. Long
                   Apartment Investment and Management Company
                                55 Beattie Place
                                 P.O. Box 1089
                        Greenville, South Carolina 29602
                                 (864) 239-1000
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           (Name, address, and telephone numbers of person authorized
       to receive notices and communications on behalf of filing persons)

                                    Copy to:

                                 Joseph A. Coco
                    Skadden, Arps, Slate, Meagher & Flom LLP
                   Four Times Square New York, New York 10036
                                 (212) 735-3000

                                       and

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

                            Calculation of Filing Fee

                  TRANSACTION VALUATION*  AMOUNT OF FILING FEE
                  ----------------------  --------------------
                      $ 2,763,917.22            $ 350.19



*        For purposes of calculating the fee only. This amount assumes the
         purchase of 13,857 units of limited partnership interest of the subject
         partnership for $199.46 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 $126.70
         per million of the aggregate amount of 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: $350.19            Filing Party: AIMCO Properties, L.P.

Form or Registration No.: Schedule TO/13E-3  Date Filed: November 5, 2004

[ ] 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

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

[ ] 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: [ ]

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                         AMENDMENT NO. 1 TO SCHEDULE TO


         This Amendment No. 1 amends and supplements the Tender Offer Statement
and Rule 13e-3 Transaction Statement on Schedule TO initially filed on November
5, 2004 (the "Schedule TO"). This Amendment No. 1 relates to the offer by AIMCO
Properties, L.P., a Delaware limited partnership, to purchase units of limited
partnership interest ("Units") of National Property Investors 4, a California
limited partnership (the "Partnership"), at a price of $199.46 per unit in cash,
subject to the conditions set forth in the Litigation Settlement Offer dated
November 5, 2004 and in the related Letter of Transmittal (which, together with
any supplements or amendments, collectively constitute the "Offer"). Copies of
the Litigation Settlement Offer and the Letter of Transmittal are filed with the
Schedule TO as Exhibits (a)(1) and (a)(2), respectively. The item numbers and
responses thereto below are in accordance with the requirements of Schedule TO,
and all section and page references are to the Litigation Settlement Offer.
Unless defined herein, capitalized terms used and not otherwise defined herein
have the respective meanings ascribed to such terms in the Litigation Settlement
Offer.

         On December 1, 2004, AIMCO Properties, L.P. issued a press release
announcing the extension of the expiration date of the Offer from midnight, New
York City time, on December 7, 2004 to midnight, New York City time, on December
15, 2004. A copy of that press release has been filed as Exhibit (a)(4) to this
Amendment No. 1.

ITEM 1. SUMMARY TERM SHEET.

         The information incorporated by reference into Item 1 of the Schedule
TO is amended and supplemented as follows:

         (1) The first paragraph of the second bullet point beginning with "The
         Settlement Fund" under "SUMMARY TERM SHEET" on page 1 is amended by
         adding the following to the end thereof:

         "In addition, if you requested exclusion from the settlement but tender
         your units, by signing the letter of transmittal, you will release us
         from claims that you would otherwise have preserved by requesting
         exclusion from the settlement class. If you did not request exclusion,
         you will release any known or unknown claims arising out of the class
         and derivative litigation if the judgment approving the settlement is
         affirmed on appeal. By executing the enclosed letter of transmittal,
         moreover, you will release those claims even if the judgment is
         reversed or otherwise vacated on appeal.  See "-Release and Assignment
         of Future Claims" below."

ITEM 4. TERMS OF THE TRANSACTION.

         The information incorporated by reference into Item 4(a) of the
Schedule TO is amended and supplemented as follows:

         (1) The third bullet point on the front cover of the Litigation
         Settlement Offer is amended by replacing the second sentence with the
         following:

         "We determined our offer price by estimating a net equity value for
         your partnership units based on a gross property value of $54,000,000
         (equal to the value determined by the independent appraisal in 2003),
         reduced by estimated prepayment penalties of $6,965,403, resulting in a
         net property value of $47,034,597.  The gross property value is the
         gross property value for your partnership's property as estimated by
         us, before reduction for any prepayment penalties."

         (2) The fourth risk factor entitled, "OUR OFFER PRICE MAY NOT REFLECT
         THE FAIR VALUE OF YOUR PARTNERSHIP'S PROPERTIES" under "RISK FACTORS"
         on page 5 is amended by replacing the first sentence with the
         following:

         "We determined our offer price by estimating a net equity value for
         your partnership units based on a gross property value of $54,000,000
         (equal to the value determined by the independent appraisal in 2003),
         reduced by estimated prepayment penalties of $6,965,403, resulting in a
         net property value of $47,034,597.  The gross property value is the
         gross property value for your partnership's property as estimated by
         us, before reduction for any prepayment penalties."

         (3) The risk factor entitled, "WE COULD DELAY ACCEPTANCE OF, AND
         PAYMENT FOR, YOUR UNITS" under "RISK FACTORS" on page 8 is amended by
         adding the following to the end thereof:

         "We will pay for or return tendered units promptly after expiration of
         the offer."

         (4) "Section 6.  Material Federal Income Tax Matters" is amended by
         adding the following to the end thereof on page 18:

                                       3

                  "Tax Consequences to the General Partner of Your Partnership
         and its Affiliates, including AIMCO Properties, L.P.  The sale of your
         units pursuant to this offer will not be a taxable transaction for the
         general partner of your partnership or its affiliates, including AIMCO
         Properties, L.P.  Consequently, the general partner of your partnership
         and its affiliates will not recognize gain or loss in connection with
         this offer.  We intend to treat the entire offer price as consideration
         paid to you for your units, regardless of whether you requested
         exclusion from the settlement.  We, like any other purchaser of units,
         will receive a tax basis in the purchased units equal to the
         consideration paid by us for the units.  This tax basis will be
         allocated over the assets owned by your partnership, and we will be
         able to take depreciation and amortization deductions to the extent
         basis is allocated to depreciable or amortizable property owned by your
         partnership."

         (5) "Section 7.  Effects of the Offer"  is amended by adding the
         following before the paragraph entitled "Accounting Treatment" on page
         19:

                  "Costs Associated with Being a Public Company.  There are
         various costs associated with being a public company, including costs
         associated with preparing, auditing and filing our periodic reports
         with the SEC.  We estimate these expenses to be approximately $33,000
         per year.  This represents approximately 13.7% of the partnership's
         general and administrative expenses and 0.51% of the partnership's
         total expenses (based on 2003 expenses of approximately $241,000 and
         $6,447,000, respectively).  In addition, as a result of the
         Sarbanes-Oxley Act of 2002, we estimate our costs will increase by
         approximately 10% beginning in 2005.  If the partnership were to
         terminate its registration under the Exchange Act, the estimated cost
         savings would be approximately $33,000 per year."

         (6) The section entitled "Determination of Offer Price" under "Section
         8. Valuation of Units" beginning on page 19 up to, but not including,
         the table on page 20 immediately preceding the section entitled
         "Comparison of Offer Price to Alternative Consideration" is amended and
         restated as follows:

                  "Determination of Offer Price.  We determined our offer price
         by estimating the liquidation proceeds that would be payable to limited
         partners if calculating a net equity value of units of limited
         partnership interest based on a valuation of your partnership's
         property. Our starting point in this process was the value of your
         partnership's property as determined by the court-appointed,
         independent appraiser in 2003. For a more a detailed description of the
         independent appraisal of your partnership's property, see "The
         Litigation Settlement Offer -- Section 8. Valuation of Units; Estimated
         Liquidation Proceeds Based on Independent Appraisal."

                  For Village of Pennbrook Apartments, we assigned it a gross
         property value of $54,000,000, which is equal to its appraised value.

                  We then deducted from the gross property value estimated
         prepayment penalties of $6,965,403 to determine its net property value.
         The following table compares the appraised value of your partnership's
         property to the net property value that we used to determine our offer
         price:

<Table>
<Caption>
                                                        GROSS        PREPAYMENT        NET
         PROPERTY                 APPRAISED VALUE   PROPERTY VALUE    PENALTY     PROPERTY VALUE
         -----------------------  ---------------   --------------   ----------   --------------
                                                                      
         Village of Pennbrook...  $    54,000,000   $   54,000,000   $6,965,403   $   47,034,597
</Table>

                  After determining the net property value, we then calculated a
         net equity value for your partnership based on such net property value
         by adding the value of the non-real estate assets of your partnership
         and deducting its liabilities, including mortgage debt and debt owed by
         your partnership to the general partner or its affiliates.

                  Finally, we allocated 93% of this net equity value to limited
         partners, which is the percentage of net proceeds that would be paid to
         limited partners in the event of a liquidation of your partnership. Our
         offer price represents the net equity value per unit determined in this
         manner, plus a pro rata portion of the settlement fund, as indicated
         below."

                                       4

         (7) The first line of the table on page 20 immediately preceding the
         section entitled "Comparison of Offer Price to Alternative
         Consideration" under "Section 8. Valuation of Units - Determination of
         Offer Price" is amended by replacing "Aggregate gross property value of
         partnership properties" with "Aggregate net property value of
         partnership properties".

         (8) "Section 8. Valuation of Units - Estimated Liquidation Proceeds
         Based on Independent Appraisal" on page 22 is amended by replacing the
         first paragraph with the following:

                  "Selection and Qualifications of Independent Appraiser.  Your
         partnership's property was appraised by American Appraisal Associates,
         Inc. ("AAA"), an independent appraiser appointed by the court.  Under
         the terms of the settlement, the independent appraiser was required to
         provide in writing its professional opinion as to the market value of
         the partnership's property as of the date of the delivery of the
         written appraisal, describing the methodologies used and other
         information which the appraiser deemed appropriate to support or
         explain its work.  The appraiser was also required to prepare an
         executive summary of the appraisal that included all material
         information.  As the appraiser was court-appointed, no special
         valuation instructions were given to the appraiser by the partnership,
         us or our affiliates.  The information set forth below was provided to
         us by AAA with respect to its appraisals."

         (9) The paragraph entitled, "Summary of Independent Appraisals of Your
         Partnership's Property" on page 24 under "Section 8. Valuation of Units
         - Estimated Liquidation Proceeds Based on Independent Appraisal" is
         amended by replacing the last sentence with the following:

         "The estimated total "as is" market value of the fee simple estate of
         your partnership's property is $54,000,000, which was the estimated
         value determined by AAA for your partnership's property and which is
         higher than the net property value of $47,034,597 as estimated by us."

         (10) The second bullet point on page 49 under "Section 19. Conditions
         to the Offer" is amended by replacing items "(v)" through "(vii)" with
         the following:

         "(v) any limitation (whether or not mandatory) by any governmental
         authority on, or any other material event which, in either case, could
         reasonably be expected to affect the extension of credit by banks or
         other lending institutions, or (vi) in the case of any of the foregoing
         existing at the time of the commencement of the offer, a material
         acceleration or worsening thereof; or"

         (11) The first sentence of the last paragraph on page 50 under "Section
         19. Conditions to the Offer" is amended by replacing the first sentence
         with the following:

              "The foregoing conditions are for our sole benefit and may be
         asserted by us regardless of the circumstances (other than
         circumstances arising out of actions or inactions by us or our
         affiliates) giving rise to such conditions or may be waived by us at
         any time in our reasonable discretion prior to the expiration of this
         offer."

                                       5


ITEM 12. EXHIBITS.

         Item 12 of the Schedule TO is amended and supplemented as follows:

         (a)(4) Press Release dated December 1, 2004.


                                       6



ITEM 13. INFORMATION REQUIRED BY SCHEDULE 13E-3.

         ITEM 7. PURPOSES, ALTERNATIVES, REASONS AND EFFECTS.

              The information incorporated by reference into Item 7(d) of
         Item 13 of the Schedule TO is amended and supplemented as follows:

              (1) "Section 6.  Material Federal Income Tax Matters" is amended
              by adding the following to the end thereof on page 18:

                       "Tax Consequences to the General Partner of Your
              Partnership and its Affiliates, including AIMCO Properties, L.P.
              The sale of your units pursuant to this offer will not be a
              taxable transaction for the general partner of your partnership or
              its affiliates, including AIMCO Properties, L.P.  Consequently,
              the general partner of your partnership and its affiliates will
              not recognize gain or loss in connection with this offer.  We
              intend to treat the entire offer price as consideration paid to
              you for your units, regardless of whether you requested exclusion
              from the settlement.  We, like any other purchaser of units, will
              receive a tax basis in the purchased units equal to the
              consideration paid by us for the units.  This tax basis will be
              allocated over the assets owned by your partnership, and we will
              be able to take depreciation and amortization deductions to the
              extent basis is allocated to depreciable or amortizable property
              owned by your partnership."

              (2) "Section 7.  Effects of the Offer"  is amended by adding the
              following before the paragraph entitled "Accounting Treatment" on
              page 19:

                       "Costs Associated with Being a Public Company.  There are
              various costs associated with being a public company, including
              costs associated with preparing, auditing and filing our periodic
              reports with the SEC.  We estimate these expenses to be
              approximately $33,000 per year. This represents approximately
              13.7% of the partnership's general and administrative expenses and
              0.51% of the partnership's total expenses (based on 2003 expenses
              of approximately $241,000 and $6,447,000, respectively).  In
              addition, as a result of the Sarbanes-Oxley Act of 2002, we
              estimate our costs will increase by approximately 10% beginning in
              2005.  If the partnership were to terminate its registration under
              the Exchange Act, the estimated cost savings would be
              approximately $33,000 per year."



                                       7

ITEM 9. REPORTS, OPINIONS, APPRAISALS AND NEGOTIATIONS

         The information incorporated by reference into Item 9(b) of Item 13
of the Schedule TO is amended and supplemented as follows:

         (1) "Section 8. Valuation of Units - Estimated Liquidation Proceeds
         Based on Independent Appraisal" on page 22 is amended by replacing the
         first paragraph with the following:

             "Selection and Qualifications of Independent Appraiser.  Your
         partnership's property was appraised by American Appraisal Associates,
         Inc. ("AAA"), an independent appraiser appointed by the court.  Under
         the terms of the settlement, the independent appraiser was required to
         provide in writing its professional opinion as to the market value
         of the partnership's property as of the date of the delivery of the
         written appraisal, describing the methodologies used and other
         information which the appraiser deemed appropriate to support or
         explain its work.  The appraiser was also required to prepare an
         executive summary of the appraisal that included all material
         information.  As the appraiser was court-appointed, no special
         valuation instructions were given to the appraiser by the partnership,
         us or our affiliates.  The information set forth below was provided to
         us by AAA with respect to its appraisals."

         (2) The paragraph entitled, "Summary of Independent Appraisals of
         Your Partnership's Property" on page 24 under "Section 8. Valuation of
         Units - Estimated Liquidation Proceeds Based on Independent Appraisal"
         is amended by replacing the last sentence with the following:

         "The estimated total "as is" market value of the fee simple estate of
         your partnership's property is $54,000,000, which was the estimated
         value determined by AAA for your partnership's property and which is
         higher than the net property value of $47,034,597 as estimated by us."

                                       8


                                    SIGNATURE

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

Date: December 1, 2004

                                          AIMCO PROPERTIES, L.P.

                                          By: AIMCO-GP, INC.
                                              Its General Partner

                                          By: /s/ Martha L. Long
                                              ---------------------------------
                                              Martha L. Long
                                              Senior Vice President

                                          APARTMENT INVESTMENT AND
                                          MANAGEMENT COMPANY

                                          By: /s/ Martha L. Long
                                              ---------------------------------
                                              Martha L. Long
                                              Senior Vice President

                                          AIMCO-GP, INC.

                                          By: /s/ Martha L. Long
                                              ---------------------------------
                                              Martha L. Long
                                              Senior Vice President

                                          NPI EQUITY INVESTMENTS, INC.

                                          By: /s/ Martha L. Long
                                              ---------------------------------
                                              Martha L. Long
                                              Senior Vice President

                                       9


                                  EXHIBIT INDEX



EXHIBIT NO.                               DESCRIPTION
- -----------    ----------------------------------------------------------------
            
   (a)(4)      Press release dated December 1, 2004.


                                       10