<PAGE>

               UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549

                                  FORM 10-K/A

[X]  ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE
     ACT OF 1934

For the fiscal year ended:  December 31, 1999
                                      OR

[_]  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES ACT
     OF 1934

For the transition period from __________ to _________.

Commission File Number: 333-79833

GREENPOINT MORTGAGE SECURITIES INC. (formerly Headlands Mortgage Securities
Inc.) (as Sponsor under the Trust Agreement, dated September 1, 1999, providing
for the Issuance of the Headlands Home Equity Loan Asset-Backed Notes,
Series 1999-1)

                      GREENPOINT MORTGAGE SECURITIES INC.
            (Exact Name of registrant as specified in its charter)

<TABLE>
          <S>                                               <C>
                     Delaware                                            68-0397342
         (State or other jurisdiction of                    (I.R.S. employer identification no.)
          incorporation or organization)

         700 Larkspur Landing Circle, Suite 240                             94939
                      Larkspur, CA                                       (Zip code)
        (Address of principal executive offices)
</TABLE>

                                (415) 925-5442
             (Registrant's telephone number, including area code)

<TABLE>
<S>                                                               <C>
Securities registered pursuant to Section 12(b) of the Act:       Securities registered pursuant to Section 12(g) of the Act:
</TABLE>

            None                                               None
     (Title of class)                                    (Title of class)

Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the Registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.  Yes [X]  No [_]

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405
of Regulation S-K is not contained herein, and will not be contained, to the
best of Registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K. [X]

State the aggregate market value of the voting stock held by non-affiliates of
Registrant.  The aggregate market value shall be computed by reference to the
price at which the stock was sold, or the average bid and asked prices of such
stock, as of specified date within 60 days prior to the date of filing:

                                Not Applicable

                     Documents incorporated by reference:

                                Not Applicable
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                                    PART IV

ITEM 14 - EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS ON FORM 8-K

          (a)  The following documents are filed as part of this report:

               3.   Exhibits:

                    Exhibit No.    Description
                    ----------     -----------

                    99.1*          Statement of Compliance of the Servicer
                                   pursuant to Section 3.09 of the Sale and
                                   Servicing Agreement.

                    99.2           Annual Servicing Report with respect to the
                                   Servicer's overall servicing operations
                                   pursuant to Section 3.10 of the Sale and
                                   Servicing Agreement.

                    99.3*          Statement of Compliance of the Issuer under
                                   the Indenture.
______________
*Previously filed.
<PAGE>

                                  SIGNATURES

      Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the Sponsor has duly caused this Report to be signed on
its behalf by the undersigned, thereunto duly authorized.


                                    By:  GREENPOINT MORTGAGE SECURITIES INC.,
                                         As Sponsor


                                         By:  /s/ Gilbert J. MacQuarrie
                                              ----------------------------------
                                         Name:  Gilbert J. MacQuarrie
                                         Title: Vice President, Chief Financial
                                                Officer, and Secretary

Date: May 31, 2000.

      Pursuant to the requirements of the Securities Exchange Act of 1934, this
Report has been signed below by the following persons on behalf of the Sponsor
and in the capacities and on the dates indicated:

<TABLE>
<CAPTION>
            Signature                                   Position                                  Date
            ----------                                 ---------                                  ----
<S>                                      <C>                                                   <C>
/s/ S.A. Ibrahim                         President and Director                                May 31, 2000
--------------------------------         (Principal Executive Officer)
S.A. Ibrahim

/s/ Becky S. Poisson                     Vice President and Director                           May 31, 2000
--------------------------------
Becky S. Poisson


/s/ Gilbert J. MacQuarrie                Vice President, Chief Financial Officer               May 31, 2000
--------------------------------         and Director
Gilbert J. MacQuarrie

/s/ Steven M. Abreu                      Vice President and Director                           May 31, 2000
--------------------------------
Steven M. Abreu


________________________________                                                               May ___, 2000
Kenneth Siprelle                         Director

________________________________                                                               May ___, 2000
John Edmonds                             Director
</TABLE>
<PAGE>

                               INDEX TO EXHIBITS
                                   Item 14(C)

Exhibit No.    Description
-----------    -----------

99.1*          Statement of Compliance of the Servicer pursuant to Section 3.09
               of the Sale and Servicing Agreement.

99.2           Annual Servicing Report with respect to the Servicer's overall
               servicing operations pursuant to Section 3.10 of the Sale and
               Servicing Agreement.

99.3*          Statement of Compliance of the Issuer under the Indenture.

______________
*Previously filed.