FIRST ADDENDUM TO LEASE
                                 BY AND BETWEEN
                                 REGENCY CENTER
                                ("THE LANDLORD")
                                       AND
                      FAIR, ISAAC AND COMPANY, INCORPORATED
                                 ("THE TENANT")

This First  Addendum to Lease,  dated  August 13, 1997  ("First  Addendum"),  is
hereby  attached  to and  incorporated  into and made a part of that Lease dated
November 14, 1996, by and between Regency Center  ("Landlord")  and Fair,  Isaac
and Company, Incorporated ("Tenant").

The following Lease provisions are hereby amended as follows:

17.      SERVICES AND UTILITIES

         Paragraph C shall be amended as follows:

         C.       Landlord shall provide Tenant a monthly  allowance of $.11 per
                  usable  square  foot  in the  Premises  (that  is,  $4,191.55;
                  $3,984.31 and $4,107.62 for the first, second and third floors
                  of  the  Building,   respectively)  for  Tenant's   electrical
                  services.  This  allowance  is  included  in the Base  Rent as
                  defined  in  Article  5 of  the  Lease.  Landlord  and  Tenant
                  recognize  that  Tenant's  electrical  service  shall  cost in
                  excess of Eleven Cents ($.11) per square foot per month due to
                  Tenant's heavy electrical and air  conditioning  requirements,
                  and  Tenant  shall pay any such  excess  costs for  electrical
                  service.

                  Tenant  shall be charged for all PG&E  charges to the building
                  over and above the monthly allowance provided above.

                  For the  first  year of  Tenant's  occupancy,  Landlord  shall
                  charge  Tenant $.11 per usable  square foot per month based on
                  the  Third  Floor  usable  square  footage  for  over-standard
                  electrical   usage  as  a  projected   expense.   This  amount
                  ($4,107.62)  shall be paid along with the monthly rent. At the
                  end of the first year of occupancy,  Landlord  shall prepare a
                  PG&E invoice analysis showing the actual cost of over-standard
                  usage by Tenant.  Landlord shall credit Tenant for any amounts
                  paid in excess of the actual




                  cost of over-standard usage. Tenant shall pay landlord for any
                  costs in excess of the total projected sum paid by Tenant over
                  the first year of  occupancy.  The  amount  paid by Tenant for
                  over-standard  electrical  usage for each  subsequent  year of
                  occupancy  shall be based on the previous year's charges and a
                  similar  accounting  between  Landlord  and Tenant  will occur
                  annually.

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

                               Regency Center, a California general partnership

                               By:               /s/ Joseph Pell
                                  ----------------------------------------------
                                           Joseph Pell, General Partner

                               Fair, Isaac and Company, Incorporated

                               By:              /s/ Michael C. Gordon
                                  ----------------------------------------------
                               Its:               Vice President