EXHIBIT 10.29
                             SIXTH ADDENDUM T0 LEASE
                                 BY AND BETWEEN
                  THE JOSEPH PELL AND EDA PELL REVOCABLE TRUST
                                 (THE LANDLORD)
                                       AND
                      FAIR, ISAAC AND COMPANY, INCORPORATED
                                  (THE TENANT)
                                      DATED
                                  JULY 1, 1993

This  Addendum to Lease dated  January 10, 1996,  ("Sixth  Addendum")  is hereby
attached  to and  incorporated  into and made a part of that lease dated July 1,
1993, by and between The Joseph and Eda Pell Revocable Trust and Fair, Isaac and
Company,  Incorporated and First Addendum to Lease by and between The Joseph and
Eda Pell Revocable Trust and Fair, Isaac and Company, Incorporated dated July 1,
1993,  and  Second  Addendum  to Lease by and  between  The  Joseph and Eda Pell
Revocable  Trust and Fair,  Isaac and Company,  Incorporated  dated  January 31,
1994,  and  Third  Addendum  to Lease by and  between  The  Joseph  and Eda Pell
Revocable Trust and Fair, Isaac and Company Incorporated dated January 31, 1994,
and Fourth  Addendum to Lease by and  between The Joseph and Eda Pell  Revocable
Trust and Fair, Isaac and Company,  Incorporated dated December 15, l994 and the
Fifth Addendum to Lease by and between the Joseph and Eda Pell  Revocable  Trust
and Fair, Isaac and Company,  Incorporated dated May 24, 1995. The parties agree
to the following terms and conditions set forth herein below:


LEASE

2.       PREMISES:  Paragraph  2 shall  be  amended  to  provide  that  Tenant's
         Premises  on the Third  Floor  shall be  increased  from  approximately
         18,115  rentable  square feet and 16,210 usable square feet  ("Original
         Premises") to 27,320 rentable square feet and 24,392 usable square feet
         ("Added  Premises")  to include the Premises  known as Suite 301 (9,205
         rentable SF and 8,182 useable SF) as shown on the attached Exhibit A.

4.       POSSESSION: Tenant shall take possession of the Added Premises on March
         18, l996, the first business day after  Headquarters  Companies vacates
         the premises in accordance with its Lease  Termination  Agreement dated
         January 9, 1996.

5.       A.       RENT:  Paragraph 5.A. of the Lease shall be amended to provide
                  that Tenant  agrees to pay Landlord as Base Rent for the Added
                  Premises the sum of Nineteen Thousand Two Hundred Thirty-eight
                  and 45/100 Dollars ($19,238.45) (9,205 rentable SF x $2.09 per
                  square  foot)  which makes the total Base Rent for the   Third
                  Floor  Premises  Fifty-five   Thousand  Four  Hundred   Sixty-
                  eight  and  45/100 Dollars ($55,468.45).

         If Fair,  Isaac  executes a  long-term  lease at Regency  Center 1 (ten
         years  minimum),  the base  rental  rate on the Added  Premises of this
         Addendum shall be the same as all the other space in the building.

7.       OPERATING EXPENSES ADJUSTMENTS: Paragraph 7 shall be amended to provide
         that  Tenant  shall  pay  26%  of  the  increase  in  Direct   Expenses
         (27,320RSF/105,000SF).

         The Base Year for the Added Premises shall be 1996.


FIRST ADDENDUM

4.       TENANT IMPROVEMENT ALLOWANCE:

         Landlord  shall provide a tenant  improvement  allowance of Twenty-five
         Thousand Dollars ($25,000.00) to be used on design and construction for
         the Added  Premises.  Landlord shall pay this allowance to Fair,  Isaac
         within thirty (30) days after occupancy of the Premises by Fair. Isaac.


SECOND ADDENDUM

5.       SERVICES AND UTILITIES

         Paragraph C shall be amended as follows:

         Tenant's monthly allowance for the entire Third Floor Premises shall be
         $3,005.20 (27,320 rentable SF x $.11).

         Tenant shall pay the amount of $2,683.12 (24,392 useable SF x $.11) per
         month as a projected expense for over-standard electrical usage.


SIXTH ADDENDUM

1.       MOVE-OUT  COMPENSATION:  In the  event  Fair,  Isaac  does  not  sign a
         long-term  lease (ten years  minimum) at Regency Center I and moves out
         of the Added  Premises,  it shall pay as  compensation on or before the
         date the Premises are vacated, six (6) months rent at the then existing
         rate. If the Added Premises are leased and occupied prior to the end of
         that six (6) month period,  the move-out  compensation shall be reduced
         for each month the space is occupied and rent is paid.

LANDLORD                    The Joseph Pell and Eda Pell Revocable Trust

                                     By:       /s/Joseph Pell
                                               -----------------------------
                                               Joseph Pell, Trustee


                                     Date:           3-7-96
                                               -----------------------------




TENANT                      Fair, Isaac and Company, Incorporated

                                     By:       /s/ Michael C. Gordon
                                               -----------------------------


                                     Its:
                                               -----------------------------



                                     Date:           3-7-96
                                               -----------------------------






                                                                   EXHIBIT 10.29

                            SEVENTH ADDENDUM TO LEASE
                                 BY AND BETWEEN
                     THE JOSEPH AND EDA PELL REVOCABLE TRUST
                                ("THE LANDLORD")
                                       AND
                      FAIR, ISAAC AND COMPANY, INCORPORATED
                                 ("THE TENANT")


         This  Seventh  Addendum to Lease  dated  November  22,  1996  ("Seventh
Addendum"),  is hereby attached to and incorporated into and made a part of that
Lease dated July 1, 1993, by and between The Joseph and Eda Pell Revocable Trust
and Fair,  Isaac and  Company,  Incorporated  as amended by a First  Addendum to
dated July 1, 1993; a Second  Addendum to Lease dated  January 31, 1994; a Third
Addendum to Lease dated January 31, 1994;  and a Fourth  Addendum to Lease dated
December  15, 1995;  a Fifth  Addendum to Lease dated May 24, 1995;  and a Sixth
Addendum to Lease dated January 10, 1996 ("the Lease"). The parties agree to the
following terms and conditions set forth herein below:

                                    Recitals

         A.  Landlord  and Tenant are  parties  to the Lease  pursuant  to which
Landlord  leased  to  Tenant  and  Tenant  leased  from  Landlord  office  space
containing  approximately  27,320 rentable square feet and 24,392 useable square
feet  comprising  part of the of the Third Floor of that certain office building
known as Regency  Center I ("Regency  I")  located at 100 Smith Ranch Road,  San
Rafael, California ("the Premises").

         B. Landlord is currently constructing a building adjacent to Regency I,
which new building will be known as Regency  Center II, and which will be leased
in its  entirety  to Tenant  pursuant to an Office  Building  Lease of even date
herewith.

         C. Landlord and Tenant now desire to amend the Lease as hereinafter set
forth.

         D. The capitalized terms herein, unless otherwise indicated, shall have
the meanings ascribed to them in the Lease.

         NOW, THEREFORE,  for good and valuable  consideration,  the receipt and
sufficiency of which are hereby acknowledged, the parties agree as follows:

         1. Paragraph 3 ("Right of First  Opportunity") of the First Addendum to
Lease is hereby deleted in its entirety.

         2. Subparagraph A and  sub-subparagraph  (i) of Paragraph 2 ("Option to
Extend")  of the First  Addendum to Lease are hereby  deleted and the  following
substituted therefor:

                  "A. Landlord grants to Tenant the option to extend the term of
                  this Lease for the Existing Premises for one (1) ten (10) year
                  period commencing upon expiration of the Term for the lease of
                  the  Existing  Premises,  upon  each and all of the  following
                  terms and conditions:"

                           "(i) Tenant gives to Landlord  and Landlord  receives
                           notice of the  exercise  of the option to extend this
                           Lease for said  additional  term no later than twelve
                           (12) months prior to the time that the option  period
                           would  commence  if the option were  exercised,  time
                           being of the  essence.  If said  notification  of the
                           exercise of said option is not so given and received,
                           this option shall automatically expire;"

         3. Except as set forth herein, the Lease shall remain unmodified and in
full force and effect.  Should  there by any  conflict  between the terms of the
Lease and the terms of this Seventh Addendum, the terms of this Seventh Addendum
shall control.

         IT WITNESS WHEREOF,  the parties have executed this Seventh Addendum to
Lease as of the date first written above.

                                 The Joseph and Eda Pell Revocable Trust


                                 By:      /s/ JOSEPH PELL
                                          --------------------------------
                                          Joseph Pell, Trustee


                                 By:      /s/ EDA PELL
                                          --------------------------------
                                          Eda Pell, Trustee


                                 Fair, Isaac and Company, Incorporated


                                 By:      /s/ MICHAEL C. GORDON
                                          --------------------------------


                                 Its:     Vice President
                                          --------------------------------





                                    Exhibit A

                    Map of the Third Floor of Regency Center

                       Approximately 9205 Rentable Sq. Ft.