<PAGE>   1
                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                -----------------

                                  FORM 10-K/A-1


  /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
                              EXCHANGE ACT OF 1934


               FOR THE TRANSITION PERIOD FROM          TO
                                              -------      ------


                         COMMISSION FILE NUMBER 1-14328

                        TRAVELERS PROPERTY CASUALTY CORP.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)



<TABLE>
<S>                                                  <C>
                 DELAWARE                                         06-1445591
(STATE OR OTHER JURISDICTION OF INCORPORATION        (I.R.S. EMPLOYER IDENTIFICATION NO.)
             OR ORGANIZATION)
</TABLE>



                  ONE TOWER SQUARE, HARTFORD, CONNECTICUT 06183
               (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES) (ZIP CODE)
                                 (860) 277-0111
              (REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE)
                                ----------------


SECURITIES REGISTERED PURSUANT TO SECTION 12(b) OF THE ACT:




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<CAPTION>
TITLE OF EACH CLASS                               NAME OF EACH EXCHANGE ON WHICH REGISTERED
-------------------                               -----------------------------------------

<S>                                               <C>
CLASS A COMMON STOCK, PAR VALUE $ .01 PER SHARE   NEW YORK STOCK EXCHANGE
6-3/4% NOTES DUE APRIL 15, 2001                   NEW YORK STOCK EXCHANGE
8.08% TRUST PREFERRED SECURITIES OF SUBSIDIARY    NEW YORK STOCK EXCHANGE
   TRUST (AND REGISTRANT'S GUARANTY
   WITH RESPECT THERETO)
8% TRUST PREFERRED SECURITIES OF SUBSIDIARY       NEW YORK STOCK EXCHANGE
   TRUST (AND REGISTRANT'S GUARANTY
   WITH RESPECT THERETO)
</TABLE>


SECURITIES REGISTERED PURSUANT TO SECTION 12(g) OF THE ACT:  NONE
<PAGE>   2
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\

THE AGGREGATE MARKET VALUE OF THE VOTING STOCK HELD BY NONAFFILIATES OF THE
REGISTRANT AS OF MARCH 3, 2000 WAS APPROXIMATELY $1.91 BILLION.

AS OF MARCH 3, 2000, 57,131,376 SHARES OF THE REGISTRANT'S CLASS A COMMON STOCK,
PAR VALUE $ .01 PER SHARE, AND 328,020,170 SHARES OF THE REGISTRANT'S CLASS B
COMMON STOCK, PAR VALUE $.01 PER SHARE, WERE OUTSTANDING.

                       DOCUMENTS INCORPORATED BY REFERENCE

CERTAIN PORTIONS OF THE REGISTRANT'S ANNUAL REPORT TO STOCKHOLDERS FOR THE
FISCAL YEAR ENDED DECEMBER 31, 1999 ARE INCORPORATED BY REFERENCE INTO PART II
OF THIS FORM 10-K.

CERTAIN PORTIONS OF THE REGISTRANT'S PROXY STATEMENT FOR THE 2000 ANNUAL MEETING
OF STOCKHOLDERS TO BE HELD ON APRIL 18, 2000 ARE INCORPORATED BY REFERENCE INTO
PART III OF THIS FORM 10-K.


<PAGE>   3

                                EXPLANATORY NOTE


      This Form 10-K/A-1 is being filed to include as an exhibit to the Form
10-K financial statements for the Travelers Group 401(k) Savings Plan pursuant
to Rule 15d-21 of the Securities Exchange Act of 1934, as amended. Other than
the related additions to the Exhibit Index, the text of Item 14 has not been
amended and speaks as of the date of the original filing of the Form 10-K.


                                     PART IV

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

     (a)      Documents filed as a part of the report:

         (1)     Financial Statements. See Index to Consolidated Financial
                 Statements and Schedules on page F-1 hereof.

         (2)    Financial Statement Schedules. See Index to Consolidated
                Financial Statements and Schedules on page F-1 hereof.

         (3)     Exhibits:

                 See Exhibit Index.
<PAGE>   4
     (b)      Reports on Form 8-K:

              There were no reports on Form 8-K filed during the quarter ended
              December 31, 1999; however, on February 29, 2000, the Company
              filed a Current Report on Form 8-K, dated February 29, 2000,
              reporting under Item 5 thereof certain information related to
              Travelers Property Casualty Corp. issuing a press release
              announcing that it had signed a letter of intent to acquire the
              surety business of Reliance Group Holdings, Inc.



                                  EXHIBIT INDEX

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<CAPTION>
EXHIBIT
NUMBER                      DESCRIPTION OF EXHIBIT
------                      ----------------------


<S>                         <C>
3.01                        Restated Certificate of Incorporation of Travelers
                            Property Casualty Corp. (the "Company"), Certificate
                            of Designations, Powers, Preferences and Rights of
                            7.5% Redeemable Preferred Stock, Series Z, of the
                            Company, Certificate of Amendment to the Restated
                            Certificate of Incorporation, filed March 7, 1997,
                            and Certificate of Amendment to the Restated
                            Certificate of Incorporation, filed April 23, 1997,
                            incorporated by reference to Exhibit 3.01 to the
                            Company's Quarterly Report on Form 10-Q for the
                            fiscal quarter ended March 31, 1997 (File
                            No.1-14328) (the "Company's 3/31/97 10-Q").

3.02                        By-Laws of the Company, effective January 19, 1999.

4.01                        Intercompany Agreement, dated as of April 2, 1996,
                            between Travelers Group Inc. and the Company,
                            incorporated by reference to Exhibit 4.1 to the
                            Company's Form S-1.

4.02.1                      Shareholders Agreement, dated as of April 2, 1996,
                            by and among the Company, The Travelers Insurance
                            Group Inc., Aetna Life and Casualty Company (now
                            known as Aetna Services, Inc.), J.P. Morgan Capital
                            Corporation, The Trident Partnership, L.P. and Fund
                            American Enterprises Holdings, Inc., incorporated by
                            reference to Exhibit 4.2 to the Company's Form S-1.

4.02.2                      Amendment to Shareholders Agreement, dated June 20,
                            1997, by and among the Company, Aetna Services,
                            Inc., J.P. Morgan Capital Corporation, The Trident
                            Partnership, L.P. and Fund American Enterprises
                            Holdings, Inc., incorporated by reference to Exhibit
                            4.02.2 to the Company's Annual Report on Form 10-K
                            for the fiscal year ended December 31, 1997 (File
                            No. 1-14328) (the "Company's 1997 10-K").

10.01.01*                   Travelers Property Casualty Corp. Capital
                            Accumulation Plan (as amended through July 23,
                            1997), incorporated by reference to Exhibit 10.01 to
                            the Company's Quarterly Report on Form 10-Q for the
                            fiscal quarter ended September 30, 1997 (File No.
                            1-14328).
</TABLE>
<PAGE>   5
<TABLE>
<CAPTION>
EXHIBIT
NUMBER                      DESCRIPTION OF EXHIBIT
------                      ----------------------


<S>                         <C>
10.01.02*                   Amendment to the Travelers Property Casualty Corp.
                            Capital Accumulation Plan (as amended through July
                            23, 1997).

10.02*                      Travelers Property Casualty Corp. 1996 Executive
                            Option Plan (as amended through March 7, 1997),
                            incorporated by reference to Exhibit 10.03 to the
                            Company's Annual Report on Form 10-K for the fiscal
                            year ended December 31, 1996 (File No. 1-14328) (the
                            "Company's 1996 10-K").

10.03*                      Travelers Property Casualty Corp. Executive
                            Performance Compensation Plan (as amended through
                            March 7, 1997), incorporated by reference to Exhibit
                            10.04 to the Company's 1996 10-K.

10.04*                      Travelers Property Casualty Corp. 1996 Deferred
                            Compensation Plan for Non-Employee Directors (as
                            amended through April 1, 1999).

10.05.1*                    Travelers Group Capital Accumulation Plan (as
                            amended through July 23, 1997), incorporated by
                            reference to Exhibit 10.02 to the Quarterly Report
                            on Form 10-Q of Travelers Group Inc. for the fiscal
                            quarter ended September 30, 1997 (File No. 1-9924)
                            (the "TRV 9/30/97 10-Q").

10.05.2*                    Amendment to Travelers Group Capital Accumulation
                            Plan (as amended through July 23, 1997),
                            incorporated by reference to Exhibit 10.08.2 to the
                            Annual Report on Form 10-K of Citigroup Inc. for the
                            fiscal year ended December 31, 1999 (File No.
                            1-9924) (the "Citigroup 12/31/99 10-K").

10.06.1*                    Travelers Group Stock Option Plan (as amended and
                            restated as of April 24, 1996), incorporated by
                            reference to Exhibit 10.02.1 to the Annual Report on
                            Form 10-K of Travelers Group Inc. for the fiscal
                            year ended December 31, 1996 (File No. 1-9924) (the
                            "TRV 1996 10-K").

10.06.2*                    Amendment No. 14 to the Travelers Group Stock Option
                            Plan, incorporated by reference to Exhibit 10.01 to
                            the Quarterly Report on Form 10-Q of Travelers Group
                            Inc. for the fiscal quarter ended September 30, 1996
                            (File No. 1-9924).

10.06.3*                    Amendment No. 15 to the Travelers Group Stock Option
                            Plan, incorporated by reference to Exhibit 10.04 to
                            the TRV 9/30/97 10-Q.


10.06.4*                    Amendment No. 16 to the Travelers Group Stock Option
                            Plan, incorporated by reference to Exhibit 10.02.4
                            to the Citigroup 12/31/99 10-K.

10.07.1*                    Travelers Group 1996 Stock Incentive Plan (as
                            amended through July 23, 1997), incorporated by
                            reference to Exhibit 10.03 to the TRV 9/30/97 10-Q.
</TABLE>
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<TABLE>
<CAPTION>
EXHIBIT
NUMBER                      DESCRIPTION OF EXHIBIT
------                      ----------------------


<S>                         <C>
10.07.2*                    Amendment to the Travelers Group 1996 Stock
                            Incentive Plan (as amended through July 23, 1997),
                            incorporated by reference to Exhibit 10.03.2 to the
                            Citigroup 12/31/99 10-K.

10.08*                      Travelers Group Inc. Retirement Benefit Equalization
                            Plan (as amended and restated as of January 2,
                            1996), incorporated by reference to Exhibit 10.04 to
                            Citigroup Inc.'s Annual Report on Form 10-K for the
                            fiscal year ended December 31, 1998 (File No.
                            1-9934) (the "Citigroup 1998 10-K").

10.09                       TAPC Tax Allocation Agreement, effective as of
                            January 1, 1996 between Travelers Group Inc. and the
                            Company, incorporated by reference to Exhibit 10.9
                            to the Company's Form S-1.

10.10                       Lease for office space at CityPlace, dated March 28,
                            1996, by and between Aetna Life and Casualty Company
                            and The Travelers Indemnity Company, incorporated by
                            reference to Exhibit 10.10 to the Company's Form
                            S-1.

10.11                       Lease for office space in Hartford, Connecticut,
                            dated as of April 2, 1996, by and between The
                            Travelers Insurance Company and The Travelers
                            Indemnity Company, incorporated by reference to
                            Exhibit 10.14 to the Company's 1996 10-K.

10.12*                      Letter Agreement, dated November 17, 1996, between
                            the Company and Stanton F. Long, incorporated by
                            reference to Exhibit 10.15 to the Company's 1996
                            10-K.


10.13*                      The Travelers Insurance Deferred Compensation Plan
                            (formerly The Travelers Corporation TESIP
                            Restoration and Non-Qualified Savings Plan) (as
                            amended December 10, 1998), incorporated by
                            reference to Exhibit 10.10 to the Citigroup 1998
                            10-K.

12.01                       Computation of Ratio of Earnings to Fixed Charges.

13.01                       Pages 17 through 55 of the 1999 Annual Report to
                            Stockholders of the Company (pagination of exhibit
                            does not correspond to pagination in the 1999 Annual
                            Report to Stockholders).

21.01                       Subsidiaries of the Registrant.

23.01                       Consent of KPMG LLP, Independent Certified Public
                            Accountants.
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<TABLE>
<CAPTION>
EXHIBIT
NUMBER                      DESCRIPTION OF EXHIBIT
------                      ----------------------


<S>                         <C>
23.02+                      Accountants' consent to incorporation by reference of report
                            filed with Exhibit 99.01

24.01                       Powers of Attorney.

27.01                       Financial Data Schedule.

99.01+                      1999 Financial Statements of the Travelers Group 401(k) Savings
                            Plan, incorporated by reference to Exhibit 99.02 to the Annual
                            Report on Form 10-K/A-1 of Citigroup Inc. for the fiscal year
                            ended December 31, 1999 (File No. 1-9924).
</TABLE>


The total amount of securities authorized pursuant to any instrument defining
rights of holders of long-term debt of the Company does not exceed 10% of the
total assets of the Company and its consolidated subsidiaries. The Company will
furnish copies of any such instrument to the Commission upon request.

Copies of any of the exhibits referred to above will be furnished at a cost of
$.25 per page (although no charge will be made for the 1999 Annual Report on
Form 10-K) to security holders who make written request therefor to Corporate
Communications, Travelers Property Casualty Corp., One Tower Square, Hartford,
Connecticut 06183.

------------------
*      Denotes a management contract or compensatory plan or arrangement
       required to be filed as an exhibit pursuant to Item 14(c) of Form 10-K.

+      Filed with Form 10-K/A-1.


Except as otherwise indicated, all exhibits were filed with the initial filing
of the Form 10-K.
<PAGE>   8
                                   SIGNATURES

         Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the registrant has duly caused this report to be signed on
its behalf by the undersigned, thereunto duly authorized, on the 28th day of
June, 2000.

                                        TRAVELERS PROPERTY CASUALTY CORP.
                                       (Registrant)


                                        By:/s/ William P. Hannon
                                        -------------------------
                                        William P. Hannon
                                        Chief Financial Officer