EXHIBIT 99.1

      CERTIFICATION OF CHIEF EXECUTIVE OFFICER AND CHIEF FINANCIAL OFFICER
                                   PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002


I, John S. Chen, certify, pursuant to 18 U.S.C. Section 1350, as adopted
pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Quarterly
Report of Sybase, Inc. on Form 10-Q for the quarterly period ended September 30,
2002 fully complies with the requirements of Section 13(a) or 15(d) of the
Securities Exchange Act of 1934 and that information contained in such Quarterly
Report fairly presents in all material respects the financial condition and
results of operations of Sybase, Inc.

                                    By:  /s/  JOHN S. CHEN
                                         ---------------------------------------
                                    Name:  John S. Chen
                                    Title: Chief Executive Officer and President

I, Pieter A. Van der Vorst, certify, pursuant to 18 U.S.C. Section 1350, as
adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the
Quarterly Report of Sybase, Inc. on Form 10-Q for the quarterly period ended
September 30, 2002 fully complies with the requirements of Section 13(a) or
15(d) of the Securities Exchange Act of 1934 and that information contained in
such Quarterly Report fairly presents in all material respects the financial
condition and results of operations of Sybase, Inc.

                                     By:  /s/  PIETER A. VAN DER VORST
                                          --------------------------------------
                                     Name:  Pieter A. Van der Vorst
                                     Title: Senior Vice President and
                                            Chief Financial Officer