<PAGE>
 
             As filed with the Securities and Exchange Commission
                               on June 20, 1997

                                              Registration No. 333-
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                               GENSYM CORPORATION
             (Exact name of registrant as specified in its charter)

        DELAWARE                               04-2932756
        (State or other jurisdiction of       (I.R.S. Employer
        incorporation or organization)         Identification Number)

        125 CAMBRIDGEPARK DRIVE
        CAMBRIDGE, MASSACHUSETTS                      02140
        (Address of Principal Executive Offices)    (Zip Code)

                           1997 STOCK INCENTIVE PLAN
                           (Full title of the Plan)

                            MR. LOWELL B. HAWKINSON
                     CHAIRMAN AND CHIEF EXECUTIVE OFFICER
                              GENSYM CORPORATION
                            125 CAMBRIDGEPARK DRIVE
                        CAMBRIDGE, MASSACHUSETTS 02140
                    (Name and address of agent for service)

                                (617) 547-2500
         (Telephone number, including area code, of agent for service)
================================================================================

                    CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
 
                                             Proposed      Proposed
Title of                                     maximum       maximum
securities         Amount      offering     aggregate     Amount of
to be              to be        price        offering    registration
registered       registered   per share       price          fee
---------------  ----------  ------------  ------------  ------------
<S>              <C>         <C>           <C>           <C>
 
Common Stock,       500,000      $5.75(1)  $2,875,000(1)  $871.21
$.01 par            shares
value per
share
</TABLE>
________________________________________________________________________________

(1)  Estimated solely for the purpose of calculating the registration fee, and
     based upon the average of the high and low prices of the Registrant's
     Common Stock as reported by the Nasdaq National Market on June 13, 1997 in
     accordance with Rules 457(c) and 457(h) of the Securities Act of 1933.

================================================================================
<PAGE>
 
PART I.  INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

          The information required by Part I of Form S-8 is included in
documents sent or given to participants in the 1997 Stock Incentive Plan of
Gensym Corporation, a Delaware corporation (the "Registrant") pursuant to Rule
428(b)(1) of the Securities Act of 1933, as amended (the "Securities Act").


PART II.  INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

          Item 3.  Incorporation of Certain Documents by Reference
                   -----------------------------------------------

          The following documents, which are filed with the Securities and
Exchange Commission (the "Commission"), are incorporated in this Registration
Statement by reference:

          (1)  The Registrant's latest annual report filed pursuant to Section
     13(a) or 15(d) of the Securities Exchange Act of 1934, as amended (the
     "Exchange Act"), or the latest prospectus filed pursuant to Rule 424(b)
     under the Securities Act that contains audited financial statements for the
     Registrant's latest fiscal year for which such statements have been filed.

          (2)  All other reports filed pursuant to Sections 13(a) or 15(d) of
     the Exchange Act since the end of the fiscal year covered by the annual
     reports or the prospectus referred to in (1) above.

          (3)  The description of the common stock of the Registrant, $.01 par
     value per share (the "Common Stock"), contained in a registration statement
     filed under the Exchange Act, including any amendment or report filed for
     the purpose of updating such description.

          All documents subsequently filed by the Registrant pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of
a post-effective amendment which indicates that all shares of Common Stock
offered hereby have been sold or which deregisters all shares of Common Stock
then remaining unsold, shall be deemed to be incorporated by reference herein
and to be part hereof from the date of the filing of such documents.

          Item 4.  Description of Securities
                   -------------------------

                   Not applicable.

          Item 5.  Interests of Named Experts and Counsel
                   --------------------------------------

                   Not applicable.

          Item 6.  Indemnification
                   ---------------

          Section 145 of the Delaware General Corporation Law provides that a
corporation has the power to indemnify a director, officer, employee or agent of
the corporation and certain other persons serving at the request of the
corporation in related capacities against amounts paid and expenses incurred in
connection with an action or proceeding to which such person is or is threatened
to be made a party by reasons of such position, if such person shall have acted
in good faith and in a manner believed to be in or not opposed to the best
interests of the corporation, and, in any criminal proceeding, if such person
had no reasonable cause to believe his or her conduct was unlawful; provided
that, in the case of actions brought by or in the right of the corporation, no
indemnification shall be made with respect to any matter as to which such person
shall have been adjudged to be liable to the corporation unless and only to the
extent that the adjudicating court determines that such indemnification is
proper under the circumstances.

                                      -1-
<PAGE>
 
          Article EIGHTH of the Registrant's Certificate of Incorporation
provides that, except to the extent that the General Corporation Law of Delaware
prohibits the elimination or limitation of liability of directors for breach of
fiduciary duty, no director of the Registrant shall be personally liable to the
Registrant or its stockholders for any monetary damages for any breach of
fiduciary duty as a director.

          Article NINTH of the Registrant's Certificate of Incorporation
provides that a director or officer of the Registrant (a) shall be indemnified
by the Registrant against all expenses (including attorneys' fees), judgments,
fines and amounts paid in settlement reasonably incurred in connection with any
litigation or other legal proceeding (other than an action by or in the right of
the Registrant) brought against such director or officer by virtue of his
position as a director or officer of the Registrant if such director or officer
acted in good faith and in a manner he reasonably believed to be in, or not
opposed to, the best interests of the Registrant, and, with respect to any
criminal action or proceeding, had no reasonable cause to believe his conduct
was unlawful and (b) shall be indemnified by the Registrant against expenses
(including attorneys' fees) and amounts paid in settlement reasonably incurred
in connection with any action by or in the right of the Registrant by virtue of
his position as a director or officer of the Registrant if such director or
officer of the Registrant acted in good faith and in a manner reasonably
believed to be in or not opposed to the best interests of the Registrant, except
that no indemnification shall be made with respect to any matter as to which
such director or officer shall have been adjudged to be liable to the
Registrant, unless and only to the extent that a court determines that, despite
such adjudication but in view of all of the circumstances of the case, such
person is fairly and reasonably entitled to indemnification for such expenses as
the court deems proper.  Notwithstanding the foregoing, to the extent that a
director or officer has been successful, on the merits or otherwise, such person
shall be indemnified against all expenses (including attorneys' fees) reasonably
incurred by such person in connection therewith.  Expenses incurred in defending
a civil or criminal action, suit or proceeding shall be advanced by the
Registrant to a director or officer, at such person's request, upon receipt of
an undertaking by the director or officer to repay the amount if it is
ultimately determined that such person is not entitled to indemnification.

          Indemnification is required to be made unless the Registrant
determines that the applicable standard of conduct required for indemnification
has not been met.  In the event of a determination by the Registrant that the
director or officer did not meet the applicable standard of conduct required for
indemnification, or if the Registrant fails to make an indemnification payment
within 60 days after such payment is claimed by such person, such person is
permitted to petition a court to make an independent determination as to whether
such person is entitled to indemnification.  As a condition precedent to the
right of indemnification, the director or officer must give the Registrant
notice of the action for which indemnity is sought and the Registrant has the
right to participate in such action or assume the defense thereof.

          Article NINTH of the Registrant's Certificate of Incorporation further
provides that the indemnification provided therein is not exclusive, and
provides that in the event that the Delaware General Corporation Law is amended
to expand the indemnification permitted to directors or officers, the Registrant
must indemnify those persons to the fullest extent permitted by such law as so
amended.

          The Registrant carries a general liability insurance policy which
covers certain liabilities of directors and officers of the Registrant arising
out of claims based on acts or omissions in their capacity as directors or
officers.

          Item 7.  Exemption from Registration Claimed
                   -----------------------------------

                   Not applicable.

          Item 8.  Exhibits
                   --------
 
                   The Exhibit Index immediately preceding the exhibits is
incorporated herein by reference.

                                      -2-
<PAGE>
 
          Item 9.  Undertakings
                   ------------

          1.   The Registrant hereby undertakes:

          (1)  To file, during any period in which offers or sales are being
     made, a post-effective amendment to this Registration Statement:

           (i)    To include any prospectus required by Section 10(a)(3)
                  of the Securities Act;

          (ii)    To reflect in the prospectus any facts or events arising
                  after the effective date of the Registration Statement (or the
                  most recent post-effective amendment thereof) which,
                  individually or in the aggregate, represent a fundamental
                  change in the information set forth in the Registration
                  Statement; and

         (iii)    To include any material information with respect to the
                  plan of distribution not previously disclosed in the
                  Registration Statement or any material change to such
                  information in the Registration Statement;

     provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if
     --------  -------                                                          
     the Registration Statement is on Form S-3 or Form S-8, and the information
     required to be included in a post-effective amendment by those paragraphs
     is contained in periodic reports filed by the Registrant pursuant to
     Section 13 or Section 15(d) of the Exchange Act that are incorporated by
     reference in the Registration Statement.

          (2)  That, for the purpose of determining any liability under the
     Securities Act, each such post-effective amendment shall be deemed to be a
     new Registration Statement relating to the securities offered therein, and
     the offering of such securities at that time shall be deemed to be the
     initial bona fide offering thereof.

          (3)  To remove from registration by means of a post-effective
     amendment any of the securities being registered which remain unsold at the
     termination of the offering.

          2.  The Registrant hereby undertakes that, for purposes of determining
any liability under the Securities Act, each filing of the Registrant's annual
report pursuant to Section 13(a) or Section 15(d) of the Exchange Act (and,
where applicable, each filing of an employee benefit plan's annual report
pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference
in the Registration Statement shall be deemed to be a new Registration Statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

          3.  Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Securities Act and
is, therefore, unenforceable.  In the event that a claim for indemnification
against such liabilities (other than the payment by the Registrant of expenses
incurred or paid by a director, officer or controlling person of the Registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Securities Act and will be governed by the final
adjudication of such issue.

                                      -3-
<PAGE>
 
                                   SIGNATURES

          Pursuant to the requirements of the Securities Act, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Cambridge, Commonwealth of Massachusetts, on 
the 14 day of June, 1997.

 
                                         GENSYM CORPORATION



                                          By:/s/  Lowell B. Hawkinson
                                             -----------------------------------
                                                  Lowell B. Hawkinson
                                                  Chairman of the Board
                                                  and Chief Executive Officer



                               POWER OF ATTORNEY

          We, the undersigned officers and directors of Gensym Corporation,
hereby severally constitute and appoint Lowell B. Hawkinson, Robert L. Moore and
Richard M. Darer, and each of them singly, our true and lawful attorneys with
full power to them, and each of them singly, to sign for us and in our names, in
the capacities indicated below, the Registration Statement on Form S-8 filed
herewith, and any and all subsequent amendments to said Registration Statement,
and generally to do all such things in our names and on our behalf and in our
capacities as officers and directors to enable Gensym Corporation to comply with
the provisions of the Securities Act of 1933, as amended, and all requirements
of the Securities and Exchange Commission, hereby ratifying and confirming our
signatures as they may be signed by our said attorneys, or any of them, to said
Registration Statement and any and all amendments thereto.

                                      -4-
<PAGE>
 
          Pursuant to the requirements of the Securities Act, this Registration
Statement has been signed below by the following persons in the capacities and
on the dates indicated.


          Signature           Title                        Date
          ---------           -----                        ----


/s/ Lowell B. Hawkinson    Chairman and,                June 14, 1997
-----------------------    Chief Executive                   
Lowell B. Hawkinson        Officer, Treasurer,
                           Secretary and      
                           Director (Principal
                           Executive Officer)  
                            


/s/ Robert L. Moore        President and                June 19, 1997
-------------------------  Director                            
Robert L. Moore, Ph.D.               


/s/ Richard M. Darer       Vice President,              June 14, 1997
-----------------------    Finance and Chief                   
Richard M. Darer           Financial Officer     
                           (Principal Financial  
                           and Accounting        
                           Officer)              
                                                 


/s/ John A. Shane          Director                     June 11, 1997
-----------------                                     
John A. Shane



/s/ Theodore G. Johnson    Director                     June 14, 1997
-----------------------                                 
Theodore G. Johnson


/s/ Thomas E. Swithenbank  Director                     June 11, 1997
-------------------------                                 
Thomas E. Swithenbank

                                      -5-
<PAGE>
 
                                 EXHIBIT INDEX
                                 -------------
                                        

Exhibit
Number    Description
-------   -----------

 4.1 (1)  Amended and Restated Certificate of Incorporation
          of the Registrant

 4.2 (1)  Amended and Restated By-Laws of the Registrant

 4.3 (2)  Specimen Stock Certificate of Common Stock
          of the Registrant

 5        Opinion of Hale and Dorr LLP
          
23.1      Consent of Hale and Dorr LLP (included in Exhibit 5)
          
23.2      Consent of Arthur Andersen LLP
          
24        Power of Attorney (included on the signature
          page of this Registration Statement)


(1)  Incorporated by reference to the Registrant's Annual Report on Form
     10-K for the fiscal year ended December 31, 1996.
(2)  Incorporated by reference to the Registration Statement on Form S-1 of
     the Registrant (Registration No. 333-80727) filed December 21, 1995.
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 19385}]
{"company-data": {"conformed-name": "GENSYM CORP", "cik": "0001005387", "assigned-sic": "7372", "irs-number": "042932756", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-29707", "film-number": "97627578"}, "business-address": {"street1": "125 CAMBRIDGE PARK DR", "city": "CAMBRIDGE", "state": "MA", "zip": "02140", "phone": "6175472500"}, "mail-address": {"street1": "125 CAMBRIDGE PARK DR", "city": "CAMBRIDGE", "state": "MA", "zip": "02140"}}
As filed with the Securities and Exchange Commission
                               on June 20, 1997

                                              Registration No. 333-
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                               GENSYM CORPORATION
             (Exact name of registrant as specified in its charter)

        DELAWARE                               04-2932756
        (State or other jurisdiction of       (I.R.S. Employer
        incorporation or organization)         Identification Number)

        125 CAMBRIDGEPARK DRIVE
        CAMBRIDGE, MASSACHUSETTS                      02140
        (Address of Principal Executive Offices)    (Zip Code)

                           1997 STOCK INCENTIVE PLAN
                           (Full title of the Plan)

                            MR. LOWELL B. HAWKINSON
                     CHAIRMAN AND CHIEF EXECUTIVE OFFICER
                              GENSYM CORPORATION
                            125 CAMBRIDGEPARK DRIVE
                        CAMBRIDGE, MASSACHUSETTS 02140
                    (Name and address of agent for service)

                                (617) 547-2500
         (Telephone number, including area code, of agent for service)
================================================================================

                    CALCULATION OF REGISTRATION FEE
Proposed      Proposed
Title of                                     maximum       maximum
securities         Amount      offering     aggregate     Amount of
to be              to be        price        offering    registration
registered       registered   per share       price          fee
---------------  ----------  ------------  ------------  ------------
Common Stock,       500,000      $5.75(1)  $2,875,000(1)  $871.21
$.01 par            shares
value per
share
________________________________________________________________________________

(1)  Estimated solely for the purpose of calculating the registration fee, and
     based upon the average of the high and low prices of the Registrant's
     Common Stock as reported by the Nasdaq National Market on June 13, 1997 in
     accordance with Rules 457(c) and 457(h) of the Securities Act of 1933.

================================================================================
PART I.  INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

          The information required by Part I of Form S-8 is included in
documents sent or given to participants in the 1997 Stock Incentive Plan of
Gensym Corporation, a Delaware corporation (the "Registrant") pursuant to Rule
428(b)(1) of the Securities Act of 1933, as amended (the "Securities Act").

PART II.  INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

          Item 3.  Incorporation of Certain Documents by Reference
                   -----------------------------------------------

          The following documents, which are filed with the Securities and
Exchange Commission (the "Commission"), are incorporated in this Registration
Statement by reference:

          (1)  The Registrant's latest annual report filed pursuant to Section
     13(a) or 15(d) of the Securities Exchange Act of 1934, as amended (the
     "Exchange Act"), or the latest prospectus filed pursuant to Rule 424(b)
     under the Securities Act that contains audited financial statements for the
     Registrant's latest fiscal year for which such statements have been filed.

          (2)  All other reports filed pursuant to Sections 13(a) or 15(d) of
     the Exchange Act since the end of the fiscal year covered by the annual
     reports or the prospectus referred to in (1) above.

          (3)  The description of the common stock of the Registrant, $.01 par
     value per share (the "Common Stock"), contained in a registration statement
     filed under the Exchange Act, including any amendment or report filed for
     the purpose of updating such description.

          All documents subsequently filed by the Registrant pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of
a post-effective amendment which indicates that all shares of Common Stock
offered hereby have been sold or which deregisters all shares of Common Stock
then remaining unsold, shall be deemed to be incorporated by reference herein
and to be part hereof from the date of the filing of such documents.

          Item 4.  Description of Securities
                   -------------------------

                   Not applicable.

          Item 5.  Interests of Named Experts and Counsel
                   --------------------------------------

                   Not applicable.

          Item 6.  Indemnification
                   ---------------

          Section 145 of the Delaware General Corporation Law provides that a
corporation has the power to indemnify a director, officer, employee or agent of
the corporation and certain other persons serving at the request of the
corporation in related capacities against amounts paid and expenses incurred in
connection with an action or proceeding to which such person is or is threatened
to be made a party by reasons of such position, if such person shall have acted
in good faith and in a manner believed to be in or not opposed to the best
interests of the corporation, and, in any criminal proceeding, if such person
had no reasonable cause to believe his or her conduct was unlawful; provided
that, in the case of actions brought by or in the right of the corporation, no
indemnification shall be made with respect to any matter as to which such person
shall have been adjudged to be liable to the corporation unless and only to the
extent that the adjudicating court determines that such indemnification is
proper under the circumstances.

                                      -1-
Article EIGHTH of the Registrant's Certificate of Incorporation
provides that, except to the extent that the General Corporation Law of Delaware
prohibits the elimination or limitation of liability of directors for breach of
fiduciary duty, no director of the Registrant shall be personally liable to the
Registrant or its stockholders for any monetary damages for any breach of
fiduciary duty as a director.

          Article NINTH of the Registrant's Certificate of Incorporation
provides that a director or officer of the Registrant (a) shall be indemnified
by the Registrant against all expenses (including attorneys' fees), judgments,
fines and amounts paid in settlement reasonably incurred in connection with any
litigation or other legal proceeding (other than an action by or in the right of
the Registrant) brought against such director or officer by virtue of his
position as a director or officer of the Registrant if such director or officer
acted in good faith and in a manner he reasonably believed to be in, or not
opposed to, the best interests of the Registrant, and, with respect to any
criminal action or proceeding, had no reasonable cause to believe his conduct
was unlawful and (b) shall be indemnified by the Registrant against expenses
(including attorneys' fees) and amounts paid in settlement reasonably incurred
in connection with any action by or in the right of the Registrant by virtue of
his position as a director or officer of the Registrant if such director or
officer of the Registrant acted in good faith and in a manner reasonably
believed to be in or not opposed to the best interests of the Registrant, except
that no indemnification shall be made with respect to any matter as to which
such director or officer shall have been adjudged to be liable to the
Registrant, unless and only to the extent that a court determines that, despite
such adjudication but in view of all of the circumstances of the case, such
person is fairly and reasonably entitled to indemnification for such expenses as
the court deems proper.  Notwithstanding the foregoing, to the extent that a
director or officer has been successful, on the merits or otherwise, such person
shall be indemnified against all expenses (including attorneys' fees) reasonably
incurred by such person in connection therewith.  Expenses incurred in defending
a civil or criminal action, suit or proceeding shall be advanced by the
Registrant to a director or officer, at such person's request, upon receipt of
an undertaking by the director or officer to repay the amount if it is
ultimately determined that such person is not entitled to indemnification.

          Indemnification is required to be made unless the Registrant
determines that the applicable standard of conduct required for indemnification
has not been met.  In the event of a determination by the Registrant that the
director or officer did not meet the applicable standard of conduct required for
indemnification, or if the Registrant fails to make an indemnification payment
within 60 days after such payment is claimed by such person, such person is
permitted to petition a court to make an independent determination as to whether
such person is entitled to indemnification.  As a condition precedent to the
right of indemnification, the director or officer must give the Registrant
notice of the action for which indemnity is sought and the Registrant has the
right to participate in such action or assume the defense thereof.

          Article NINTH of the Registrant's Certificate of Incorporation further
provides that the indemnification provided therein is not exclusive, and
provides that in the event that the Delaware General Corporation Law is amended
to expand the indemnification permitted to directors or officers, the Registrant
must indemnify those persons to the fullest extent permitted by such law as so
amended.

          The Registrant carries a general liability insurance policy which
covers certain liabilities of directors and officers of the Registrant arising
out of claims based on acts or omissions in their capacity as directors or
officers.

          Item 7.  Exemption from Registration Claimed
                   -----------------------------------

                   Not applicable.

          Item 8.  Exhibits
                   --------
 
                   The Exhibit Index immediately preceding the exhibits is
incorporated herein by reference.

                                      -2-
Item 9.  Undertakings
                   ------------

          1.   The Registrant hereby undertakes:

          (1)  To file, during any period in which offers or sales are being
     made, a post-effective amendment to this Registration Statement:

           (i)    To include any prospectus required by Section 10(a)(3)
                  of the Securities Act;

          (ii)    To reflect in the prospectus any facts or events arising
                  after the effective date of the Registration Statement (or the
                  most recent post-effective amendment thereof) which,
                  individually or in the aggregate, represent a fundamental
                  change in the information set forth in the Registration
                  Statement; and

         (iii)    To include any material information with respect to the
                  plan of distribution not previously disclosed in the
                  Registration Statement or any material change to such
                  information in the Registration Statement;

     provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if
     --------  -------                                                          
     the Registration Statement is on Form S-3 or Form S-8, and the information
     required to be included in a post-effective amendment by those paragraphs
     is contained in periodic reports filed by the Registrant pursuant to
     Section 13 or Section 15(d) of the Exchange Act that are incorporated by
     reference in the Registration Statement.

          (2)  That, for the purpose of determining any liability under the
     Securities Act, each such post-effective amendment shall be deemed to be a
     new Registration Statement relating to the securities offered therein, and
     the offering of such securities at that time shall be deemed to be the
     initial bona fide offering thereof.

          (3)  To remove from registration by means of a post-effective
     amendment any of the securities being registered which remain unsold at the
     termination of the offering.

          2.  The Registrant hereby undertakes that, for purposes of determining
any liability under the Securities Act, each filing of the Registrant's annual
report pursuant to Section 13(a) or Section 15(d) of the Exchange Act (and,
where applicable, each filing of an employee benefit plan's annual report
pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference
in the Registration Statement shall be deemed to be a new Registration Statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

          3.  Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Securities Act and
is, therefore, unenforceable.  In the event that a claim for indemnification
against such liabilities (other than the payment by the Registrant of expenses
incurred or paid by a director, officer or controlling person of the Registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Securities Act and will be governed by the final
adjudication of such issue.

                                      -3-
SIGNATURES

          Pursuant to the requirements of the Securities Act, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Cambridge, Commonwealth of Massachusetts, on 
the 14 day of June, 1997.

 
                                         GENSYM CORPORATION

                                          By:/s/  Lowell B. Hawkinson
                                             -----------------------------------
                                                  Lowell B. Hawkinson
                                                  Chairman of the Board
                                                  and Chief Executive Officer

                               POWER OF ATTORNEY

          We, the undersigned officers and directors of Gensym Corporation,
hereby severally constitute and appoint Lowell B. Hawkinson, Robert L. Moore and
Richard M. Darer, and each of them singly, our true and lawful attorneys with
full power to them, and each of them singly, to sign for us and in our names, in
the capacities indicated below, the Registration Statement on Form S-8 filed
herewith, and any and all subsequent amendments to said Registration Statement,
and generally to do all such things in our names and on our behalf and in our
capacities as officers and directors to enable Gensym Corporation to comply with
the provisions of the Securities Act of 1933, as amended, and all requirements
of the Securities and Exchange Commission, hereby ratifying and confirming our
signatures as they may be signed by our said attorneys, or any of them, to said
Registration Statement and any and all amendments thereto.

                                      -4-
Pursuant to the requirements of the Securities Act, this Registration
Statement has been signed below by the following persons in the capacities and
on the dates indicated.

          Signature           Title                        Date
          ---------           -----                        ----

/s/ Lowell B. Hawkinson    Chairman and,                June 14, 1997
-----------------------    Chief Executive                   
Lowell B. Hawkinson        Officer, Treasurer,
                           Secretary and      
                           Director (Principal
                           Executive Officer)  
                            

/s/ Robert L. Moore        President and                June 19, 1997
-------------------------  Director                            
Robert L. Moore, Ph.D.               

/s/ Richard M. Darer       Vice President,              June 14, 1997
-----------------------    Finance and Chief                   
Richard M. Darer           Financial Officer     
                           (Principal Financial  
                           and Accounting        
                           Officer)              
                                                 

/s/ John A. Shane          Director                     June 11, 1997
-----------------                                     
John A. Shane

/s/ Theodore G. Johnson    Director                     June 14, 1997
-----------------------                                 
Theodore G. Johnson

/s/ Thomas E. Swithenbank  Director                     June 11, 1997
-------------------------                                 
Thomas E. Swithenbank

                                      -5-
EXHIBIT INDEX
                                 -------------
                                        

Exhibit
Number    Description
-------   -----------

 4.1 (1)  Amended and Restated Certificate of Incorporation
          of the Registrant

 4.2 (1)  Amended and Restated By-Laws of the Registrant

 4.3 (2)  Specimen Stock Certificate of Common Stock
          of the Registrant

 5        Opinion of Hale and Dorr LLP
          
23.1      Consent of Hale and Dorr LLP (included in Exhibit 5)
          
23.2      Consent of Arthur Andersen LLP
          
24        Power of Attorney (included on the signature
          page of this Registration Statement)

(1)  Incorporated by reference to the Registrant's Annual Report on Form
     10-K for the fiscal year ended December 31, 1996.
(2)  Incorporated by reference to the Registration Statement on Form S-1 of
     the Registrant (Registration No. 333-80727) filed December 21, 1995.