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                                                                    EXHIBIT 31.1

                    CERTIFICATION OF CHIEF EXECUTIVE OFFICER

          PURSUANT TO SECTION 302(a) OF THE SARBANES-OXLEY ACT OF 2002

I, Steven D. Goldby, Chief Executive Officer of Symyx Technologies, Inc.,
certify that:

1.   I have reviewed this Annual Report on Form 10-K of Symyx Technologies,
     Inc.;

2.   Based on my knowledge, this annual report does not contain any untrue
     statement of a material fact or omit to state a material fact necessary to
     make the statements made, in light of the circumstances under which such
     statements were made, not misleading with respect to the period covered by
     this annual report;

3.   Based on my knowledge, the financial statements, and other financial
     information included in this annual report, fairly present in all material
     respects the financial condition, results of operations and cash flows of
     the registrant as of, and for, the periods presented in this annual report;

4.   The registrant's other certifying officers and I are responsible for
     establishing and maintaining disclosure controls and procedures (as defined
     in Exchange Act Rules 13a-14 and 15d-14) for the registrant and we have:

          a)   designed such disclosure controls and procedures to ensure that
               material information relating to the registrant, including its
               consolidated subsidiaries, is made known to us by others within
               those entities, particularly during the period in which this
               annual report is being prepared;

          b)   evaluated the effectiveness of the registrant's disclosure
               controls and procedures as of a date within 90 days prior to the
               filing date of this annual report (the "Evaluation Date"); and

          c)   presented in this annual report our conclusions about
               effectiveness of the disclosure controls and procedures based on
               our evaluation as of the Evaluation Date;

5.   The registrant's other certifying officers and I have disclosed, based on
     our most recent evaluation, to the registrant's auditors and the audit
     committee of registrant's board of directors (or persons performing the
     equivalent functions):

          a)   all significant deficiencies in the design or operation of
               internal controls which could adversely affect the registrant's
               ability to record, process, summarize and report financial data
               and have identified for the registrant's auditors any material
               weaknesses in internal controls; and

          b)   any fraud, whether or not material, that involves management or
               other employees who have a significant role in the registrant's
               internal controls; and

6.   The registrant's other certifying officers and I have indicated in this
     annual report whether or not there were significant changes in internal
     controls or in other factors that could significantly affect internal
     controls subsequent to the date of our most recent evaluation, including
     any corrective actions with regard to significant deficiencies and material
     weaknesses.

Date: March 8, 2004                            By: /s/ Steven D. Goldby
                                                   ----------------------------
                                                   Steven D. Goldby
                                                   Chairman of the Board,
                                                   Chief Executive Officer

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