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                                                                    EXHIBIT 5.01








                                October 11, 1996


HNC Software Inc.
5930 Cornerstone Court West
San Diego, California 92121

Gentlemen/Ladies:

         At your request, we have examined the Registration Statement on Form
S-8 (the "REGISTRATION STATEMENT") to be filed by you with the Securities and
Exchange Commission on or about October 14, 1996 in connection with the
registration under the Securities Act of 1933, as amended, of 248,504 shares of
your Common Stock (the "Stock") which are issuable upon the exercise of options
originally granted by Risk Data Corporation and assumed by you in connection
with the merger of your wholly-owned subsidiary, HNC Merger Corp., with and into
Risk Data Corporation (the "ASSUMED OPTIONS").

         In rendering this opinion, we have examined the following:

         (1)      the Registration Statement, together with the Exhibits filed
                  as a part thereof;

         (2)      the Prospectuses prepared in connection with the Assumed
                  Options and with the Registration Statement;

         (3)      the minutes of meetings and actions by written consent of the
                  Board of Directors that are contained in your minute books,
                  that are in our possession under which the Assumed Options
                  were approved for assumption by you; and

         (4)      the Agreement and Plan of Reorganization dated July 19, 1996,
                  and the Agreement of Merger and the Escrow Agreement, both
                  dated August 30, 1996, that were entered into in connection
                  with the acquistion of Risk Data Corporation, under which the
                  Assumed Options were assumed by you.

         In our examination of documents for purposes of this opinion, we have
assumed, and express no opinion as to, the genuineness of all signatures on
original documents, the authenticity of all documents submitted to us as
originals, the conformity to originals of all documents submitted to us as
copies, the lack of any undisclosed terminations, modifications, waivers or
amendments to any documents reviewed by us and the due execution and delivery of
all documents where due execution and delivery are prerequisites to the
effectiveness thereof.

         As to matters of fact relevant to this opinion, we have relied solely
upon our examination of the documents referred to above and have assumed the
current accuracy and completeness of the information obtained from public
officials and records included in the documents referred to above. We have made
no independent investigations or other attempts to verify the accuracy of any of
such information or to determine the existence or non-existence of any other
factual matters; however, we are not aware of any facts that would lead us to
believe that the opinion expressed herein is not accurate.

         Based upon the foregoing, it is our opinion that the 248,504 shares of
Stock that may be issued and sold by you pursuant to the Assumed Options, when
issued and sold in the manner referred to in the Prospectus associated with the
Registration Statement and in accordance with the terms of the Assumed Options,
will be legally issued, fully paid and nonassessable.


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         We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to all references to us, if any, in the
Registration Statement and any amendments thereto.

         This opinion speaks only as of its date and is intended solely for the
your use as an exhibit to the Registration Statement for the purpose of the
above sale of the Stock and is not to be relied upon for any other purpose.

                                                     Very truly yours,



FENWICK & WEST LLP