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                                                                    EXHIBIT 10.2

                            SECURED PROMISSORY NOTE
                            -----------------------

                                                                 October 1, 1997
$100,000                                                Cambridge, Massachusetts

     FOR VALUE RECEIVED, Stephen R. Quehl (the "Maker"), promises to pay to
Gensym Corporation ("Gensym"), or order, at the offices of Gensym or at such
other place as the holder of this Note may designate, the principal sum of
$100,000, together with interest on the unpaid principal balance of this Note
from time to time outstanding at the rate of 8.5% per year (the prime rate of
lending of BankBoston, N.A., in effect on the date hereof).

     Principal and interest shall be due and payable on October 1, 2000,
provided, however, that in the event the Maker has continuously been employed by
Gensym from the date hereof until October 1, 2000, all principal and interest
due and payable under this Note shall be forgiven by Gensym on October 1, 2000,
and further provided, however, that in the event the Maker's employment with
Gensym is involuntarily terminated by Gensym for any reason other than gross
misconduct or negligence prior to October 1, 2000, then Gensym shall forgive
such portion of the principal and interest due and payable under this Note as is
equal to such principal and interest multiplied by a fraction, the numerator of
which will equal the number of full months during which the Maker was employed
by Gensym and the denominator of which will be 36.

     Notwithstanding the foregoing, all principal and interest due and payable
under this Note shall be forgiven by Gensym in the event that, prior to October
1, 2000, (i) there is an Acquisition (as defined below) of Gensym in which the
consideration per share received by holders of Gensym Common Stock in the
Acquisition is less than $5.8735, (ii) at the time of the Acquisition, the Maker
has been continuously employed by Gensym from the date hereof and (iii) after
the Acquisition, the Maker is not retained by or offered a position with the
surviving or acquiring entity (the "Acquiror"), with responsibilities and
compensation at least equivalent to his responsibilities and compensation with
Gensym on the day before the execution of the definitive agreement with respect
to the Acquisition.

     For the purposes of this Note, "Acquisition" shall mean any merger or
consolidation which results in the voting securities of Gensym outstanding
immediately prior thereto representing immediately thereafter (either by
remaining outstanding or by being converted into voting securities of the
Acquiror) less than a majority of the combined voting power of the voting
securities of the Acquiror outstanding immediately after such merger or
consolidation.

     Interest on this Note shall be computed on the basis of a year of 365 days
for the actual number of days elapsed.  All payments by the Maker under this
Note shall be in immediately available funds.

     Payment of this Note is secured by a security interest in certain property
of the 

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Maker (the "Collateral") pursuant to a pledge agreement of even date herewith
between the Maker and Gensym (the "Pledge Agreement").

     This Note shall become immediately due and payable without notice or demand
upon the occurrence at any time of any of the following events of default
(individually, "an Event of Default" and collectively, "Events of Default"):

     (1) default in the payment or performance of this or any other liability or
         obligation of the Maker to the holder, including the payment when due
         of any principal, premium or interest under this Note;

     (2) death, incapacity or insolvency of the Maker;

     (3) the termination of the Maker's employment with Gensym (subject to the
         reduction in principal and interest due and payable under this Note
         provided for in the second paragraph of this Note);
 
     (4) the occurrence of any event of default under the Pledge Agreement;

     (5) the institution by or against the Maker or any indorser or guarantor of
         this Note of any proceedings under the United States Bankruptcy Code or
         any other federal or state bankruptcy, reorganization, receivership,
         insolvency or other similar law affecting the rights of creditors
         generally or the making by the Maker or any indorser or guarantor of
         this Note of a composition or an assignment or trust mortgage for the
         benefit of creditors; or

     (6) determination by the holder that it is insecure with respect to the
         payment of any obligation of the Maker to the holder.

     Upon the occurrence of an Event of Default, the holder shall have then, or
at any time thereafter, all of the rights and remedies afforded by the Uniform
Commercial Code as from time to time in effect in the Commonwealth of
Massachusetts or afforded by other applicable law.

     Every amount overdue under this Note shall bear interest from and after the
date on which such amount first became overdue at an annual rate which is two
(2) percentage points above the rate per year specified in the first paragraph
of this Note (the "Default Rate").  Such interest on overdue amounts under this
Note shall be payable on demand and shall accrue and be compounded monthly until
the obligation of the Maker with respect to the payment of such interest has
been discharged (whether before or after judgment).

     In no event shall any interest charged, collected or reserved under this
Note exceed the maximum rate then permitted by applicable law and if any such
payment 

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is paid by the Maker, then such excess sum shall be credited by the holder as a
payment of principal.

     All payments by the Maker under this Note shall be made without set-off or
counterclaim and be free and clear and without any deduction or withholding for
any taxes or fees of any nature whatever, unless the obligation to make such
deduction or withholding is imposed by law.  The Maker shall pay and save the
holder harmless from all liabilities with respect to or resulting from any delay
or omission to make any such deduction or withholding required by law.

     Whenever any amount is paid under this Note, all or part of the amount paid
may be applied to principal, premium or interest in such order and manner as
shall be determined by the holder in its discretion.

     No reference in this Note to the Pledge Agreement or any guaranty shall
impair the obligation of the Maker, which is absolute and unconditional, to pay
all amounts under this Note strictly in accordance with the terms of this Note.

     The Maker agrees to pay on demand all costs of collection, including
reasonable attorneys' fees, incurred by the holder in enforcing the obligations
of the Maker under this Note.

     No delay or omission on the part of the holder in exercising any right
under this Note or the Pledge Agreement shall operate as a waiver of such right
or of any other right of such holder, nor shall any delay, omission or waiver on
any one occasion be deemed a bar to or waiver of the same or any other right on
any future occasion.  The Maker and every indorser or guarantor of this Note
regardless of the time, order or place of signing waives presentment, demand,
protest and notices of every kind and assents to any extension or postponement
of the time of payment or any other indulgence, to any substitution, exchange or
release of collateral, and to the addition or release of any other party or
person primarily or secondarily liable.

     This Note may be prepaid in whole or in part at any time or from time to
time upon five (5) days' prior written notice with the consent of the holder,
with the giving of such consent to be in the sole discretion of the holder.  Any
such prepayment shall be without premium or penalty.

     None of the terms or provisions of this Note may be excluded, modified or
amended except by a written instrument duly executed on behalf of the holder
expressly referring to this Note and setting forth the provision so excluded,
modified or amended.

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     All rights and obligations hereunder shall be governed by the laws of the
Commonwealth of Massachusetts and this Note is executed as an instrument under
seal.

                              /s/ Stephen R. Quehl
                              __________________________
                              Stephen R. Quehl


Witness:

___________________________

Name:_____________________

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