GENSYM CORPORATION
                                52 Second Avenue
                        Burlington, Massachusetts  01803

                               November 15, 2001


VIA EDGAR

Securities and Exchange Commission
450 Fifth Street, N.W.
Judiciary Plaza
Washington, D.C.  20549
Attention:  Barry N. Summer
            Loryn Zerner

       Re:   Gensym Corporation
             Rule 477 Application for Withdrawal
             Registration Statement on Form S-3 (File No. 333-68252)
             -------------------------------------------------------

Ladies and Gentlemen:

       Pursuant to Rules 477(a) and (b) promulgated under the Securities Act of
1933, as amended, Gensym Corporation (the "Company") hereby requests withdrawal
of the above-referenced registration statement on Form S-3 (the "Registration
Statement").  It is the Company's understanding that this application to
withdraw the Registration Statement will be deemed granted upon filing with the
Securities and Exchange Commission, unless the Commission objects within 15 days
after the filing hereof.

       The Company requests withdrawal of the Registration Statement because it
has determined not to proceed with the transactions contemplated thereby.  The
Company confirms that no securities of the Company have been sold under the
Registration Statement.

       If you have any questions or comments or require further information or
documentation, please do not hesitate to contact the undersigned at (781) 265-
7100 or Corey C. DuFresne, Esq., of Hale and Dorr LLP, outside counsel to the
Company, at (617) 526-6000.

                                    Sincerely,


                                    GENSYM CORPORATION


                                    By:   /s/ Jeffrey A. Weber
                                         ---------------------
                                         Jeffrey A. Weber
                                         Vice President, Finance and
                                         Chief Financial Officer