EXHIBIT 5.1

                                  July 31, 2001


Fair, Isaac and Company, Incorporated
200 Smith Ranch Road
San Rafael, CA  94903


     Re:     Registration Statement on Form S-8 for the Fair, Isaac and Company,
             Incorporated 1992 Long-Term Incentive Plan


Ladies and Gentlemen:

     With  reference  to the  Registration  Statement on Form S-8 to be filed by
Fair, Isaac and Company,  Incorporated,  a Delaware corporation (the "Company"),
with the  Securities  and Exchange  Commission  under the Securities Act of 1933
relating to 581,562  additional  shares of the Company's common stock, par value
$0.01 per share (the "Common  Stock"),  issuable  pursuant to the Company's 1992
Long-Term Incentive Plan (the "Plan"), it is our opinion that such shares of the
Common Stock of the Company,  when issued and sold in accordance  with the Plan,
will be legally issued, fully paid and nonassessable.

     We hereby  consent to the filing of this  opinion with the  Securities  and
Exchange  Commission  as  Exhibit  5.1  and  Exhibit  23.1  to the  Registration
Statement.


                                Very truly yours,

                                /s/ PILLSBURY WINTHROP LLP