Exhibit #10.38

                                                     December 16, 1998


Ms. Judith W. Isaac
73126 Montera Circle South
Palm Desert, CA  92260-6625
(760) 341-6625

Dear Judy:

         This letter is intended to serve as the  definitive  agreement  between
Fair,  Isaac and Company,  Inc.  (the " Company") and you and your children with
respect to possible transactions  involving the Company's common stock. The term
"Founding Shareholder" as used in this letter agreement refers to you.

         The terms of our agreement are as follows:

(A)      The Company hereby grants the Founding  Shareholder's  estate the right
         to sell to the Company,  and Company agrees to purchase,  up to 250,000
         shares of Fair,  Isaac stock,  but not exceeding $10 million in amount,
         upon the Founding Shareholder's death. (This right is commonly known as
         a "put".) The Founding  Shareholder's estate must notify the Company of
         the number of shares to be sold to the Company  within 60 calendar days
         after the date of death,  and the  Company  must pay for the shares not
         later than nine months after the date of death.

         The  purchase  price of this stock shall be based on the average of the
         "last trade" prices quoted by the New York Stock Exchange (NYSE) during
         the 30 calendar days ending on the date of death.

         This "put"  right will expire on October 31,  2003,  unless  terminated
         earlier as set forth herein.

(B)      The Founding  Shareholder  and her children grants the Company a "right
         of first refusal" to purchase up to 500,000 shares of Fair, Isaac stock
         effective  on the date of this  agreement.  Under this  "right of first
         refusal"  Founding  Shareholder  and her  children  shall  not sell any
         shares,  excepting permitted  transactions by the Founding  Shareholder
         described below, without first giving notice to the Company.

         The notice of sale shall  include the exact and  complete  terms of the
         proposed sale and will have attached thereto a photocopy of an executed
         bona fide offer and if  applicable,  counteroffer.  For a period of ten
         (10)  business days after receipt by


<PAGE>
FOUNDING SHAREHOLDER STOCK AGREEMENT
December 16, 1998
Page 2

         the Company of the notice of sale,  the Company shall have the right to
         give the  Founding  Shareholder  or her child,  as the case may be, (a)
         notice of the  Company's  exercise of the right to purchase the shares,
         on the same terms, price and conditions as set forth in notice of sale,
         or (b)  notice  declining  to  exercise  its right of first  refusal to
         purchase the shares. In the event that Company declines to exercise its
         right to  purchase  these  shares and  thereafter  there are changes in
         terms,  price or  conditions  between the Founding  Shareholder  or her
         child (as the case may be) and the prospective purchaser,  the right of
         first refusal shall reapply to these shares.

         In the event of the Founding  Shareholder's  death,  any shares sold by
         the estate under (A), above, would count against the 500,000 shares.

         The  Company's  right of first refusal would not apply to the following
         types of transactions by the Founding Shareholder:

                  o    Gift,  sale or  transfer  to the  Founding  Shareholder's
                       children.

                  o    Gift,  sale or transfer in the  aggregate of no more than
                       20,000   shares   to   persons   who  are  not   Founding
                       Shareholder's  children during the period that this right
                       of first refusal is in effect.

                  o    Sales  on the NYSE  under  the  volume  limit of Rule 144
                       adopted under the Securities Act of 1933, as amended,  or
                       any similar  successor  federal statute and the rules and
                       regulations  thereunder,  all as  the  same  shall  be in
                       effect from time to time limit ("Rule 144").

                  o    Funding  of  charitable  remainder  and  charitable  lead
                       trusts.

                  o    Purchase  of  shares by the Fair,  Isaac  Employee  Stock
                       Ownership Plan.

         The Company's right of first refusal will expire on October 31, 2003.

(C)      The Founding Shareholder and her children agree to reduce the number of
         Fair,  Isaac shares they hold from the current  level to a number below
         1.4 million  shares by October 31, 2001. The Founding  Shareholder  and
         her  children  agree to achieve  this result in part by disposing of at
         least 150,000  shares during the period from the date of this letter to
         September 30, 1999,  and a cumulative  total of at least 300,000 shares
         by September 30, 2000. The types of  dispositions  contemplated by this
         section include  dispositions in which the Founding Shareholder and her
         family retain no beneficial  interest in the shares, such as gift, sale
         or  other  transfer  to  persons  who  are not  Founding  Shareholder's
         children;  sales on the NYSE  under  Rule 144;  funding  of  charitable
         remainder and charitable lead trusts;  and sales of shares to the Fair,
         Isaac Employee Stock Ownership Plan.

         If the  Founding  Shareholder  and her family  have not  brought  their
         combined  holdings  below the required  applicable  level at any of the
         foregoing three


<PAGE>
FOUNDING SHAREHOLDER STOCK AGREEMENT
December 16, 1998
Page 3

         milestone dates listed above,  the right of the Founding  Shareholder's
         estate to sell  shares to the  Company,  as set forth in  section  (A),
         above, shall terminate on that date without notice by Company.

(D)      For a period  of one  year  from  the  date of the  agreement,  if this
         agreement  would  prevent  the  Company  from  applying  the pooling of
         interests' method of accounting to a business combination,  the Company
         may rescind this agreement at its sole option, by written notice.

(E)      If the Company does rescind this agreement  under section (D) above and
         if the Founding  Shareholder  dies on or before  October 31, 2003,  the
         Founding  Shareholder's  estate may  require the Company to approve the
         registration  of between 250,000 and 500,000 shares held by the estate.
         The term "registration" refers to a registration of securities for sale
         effected by preparing  and filing a  registration  statement or similar
         document  in  compliance  with  the  Securities  Act of  1933  and  the
         declaration or ordering of effectiveness of such registration statement
         or document by the Securities and Exchange Commission.

(F)      The Board of Directors of the Company has, by duly adopted  resolution,
         authorized the execution of this agreement on behalf of the Company.

(G)      The Company and the Founding Shareholder,  her children and estate will
         give  notice  under this  agreement  in writing  and the notice will be
         deemed  effectively  given upon  personal  delivery  to the party to be
         notified, or overnight courier service, or upon deposit with the United
         States Post Office,  by registered or certified  mail,  postage prepaid
         and  addressed,  if  to  the  Company,  at  Fair,  Isaac  and  Company,
         Incorporated, 120 North Redwood Drive, San Rafael, CA 94903, Attention:
         General  Counsel;  if to Founding  Shareholder or her children,  at the
         address shown in this letter; and, if to her estate, at the address for
         notice  specified  by the estate in  writing.  Any party may change its
         address  for  notices by giving  written  notice of such  change to the
         other party or parties.

(H)       This agreement  shall inure to the benefit of, and shall be and become
          binding on, the heirs, executors,  administrators,  and assigns of the
          respective parties,  but neither this agreement nor any of the rights,
          interests or  obligations  hereunder may be assigned,  transferred  or
          delegated by Founding  Shareholder or her children to any person other
          than  executors,   administrators,   legatees  or  heirs  of  Founding
          Shareholder  upon the death of such Founding  Shareholder.  Each of us
          will  pay  our  own  fees  and  expenses   incurred  incident  to  the
          preparation and carrying out of the transactions  contemplated by this
          agreement.


<PAGE>


FOUNDING SHAREHOLDER STOCK AGREEMENT
December 16, 1998
Page 4

(I)       This agreement  contains the entire  understanding of the parties with
          respect  to the  matters  covered  herein  and  supersedes  all  prior
          agreements and  understandings,  written or oral,  between the parties
          relating to the subject matter hereof.  Any additions or modifications
          to this agreement must be made in writing and must be signed on behalf
          of all the parties to this agreement.

(J)       The laws of the State of California (irrespective of its choice of law
          principles)  shall  govern  this  agreement.  This  Agreement  may  be
          executed in two or more counterparts, each of which shall be deemed an
          original,  but all of which together shall constitute one and the same
          instrument.

         If this letter correctly sets forth our understanding, please sign both
copies of this letter and have them signed by each of your children,  and return
one fully signed copy to me.

                                            Very truly yours,


                                            Peter L. McCorkell
                                            Senior Vice President and
                                            General Counsel


Agreed to this      day of December, 1998
               ----


------------------------------              -----------------------------
Ms. Judith W. Isaac                         Kenneth W. Isaac


------------------------------              ------------------------------
Cynthia W. Isaac                            Timothy E. Isaac