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                                                                    EXHIBIT 31.1

                                  CERTIFICATION

      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 report;

3.    Based on my knowledge, the financial statements, and other financial
      information included in this 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 report;

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

            a)    Designed such disclosure controls and procedures, or caused
                  such disclosure controls and procedures to be designed under
                  our supervision, 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 and presented in this report our
                  conclusions about the effectiveness of the disclosure controls
                  and procedures, as of the end of the period covered by this
                  report based on such evaluation; and

            c)    Disclosed in this report any change in the registrants
                  internal control over financial reporting that occurred during
                  the registrant's most recent fiscal quarter (the registrant's
                  fourth quarter in the case of an annual report) that has
                  materially affected, or is reasonably likely to materially
                  affect, the registrant's internal control over financial
                  reporting; and

5.    The registrant's other certifying officer(s) and I have disclosed, based
      on our most recent evaluation of internal controls over financial
      reporting, 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 and material weaknesses in the
                  design or operation of internal controls over financial
                  reporting which are reasonably likely to adversely affect the
                  registrant's ability to record, process, summarize and report
                  financial information; 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 over financial reporting.

Date: April 15, 2004                       By:   /s/ Steven D. Goldby
                                           ---------------------------------
                                           Steven D. Goldby
                                           Chairman of the Board,
                                           Chief Executive Officer