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                                                                    Exhibit 5.01




                                 August 21, 1998




HNC Software Inc.
5930 Cornerstone Court West
San Diego, California 92121-3728


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 (the "Commission") on or about August 24, 1998 in connection
with the registration under the Securities Act of 1933, as amended, of an
aggregate of 1,000,000 additional shares of the Common Stock, $0.001 par value
(the "Common Stock") of HNC Software Inc., a Delaware corporation (the
"Company"), subject to issuance by the Company under its 1995 Equity Incentive
Plan, as amended through May 21, 1998 (the "HNC 1995 Plan).

         In rendering this opinion, we have examined the following:

         (1)      the Company's registration statement on Form S-1 (File Number
                  33-91932) filed with and declared effective by the Commission
                  on June 20, 1995, together with the Exhibits filed as a part
                  thereof;

         (2)      the Company's registration statement on Form 8-A filed with
                  the Commission on May 26, 1995, together with the order of
                  effectiveness issued by the Commission therefor on June 20,
                  1995;

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

         (4)      the HNC 1995 Plan and related award grant and exercise
                  agreement forms;

         (5)      the Prospectus prepared in connection with the Registration
                  Statement;

         (6)      the Restated Certificate of Incorporation of the Company filed
                  with the Delaware Secretary of State on June 13, 1996;

         (7)      the Bylaws of the Company, as certified by the Company's
                  Secretary on August 5, 1998;

         (8)      the minutes of meetings and actions by written consent of the
                  stockholders and Board of Directors of the Company that are
                  contained in the Company's minute books that are in our
                  possession;

         (9)      the stock records for the Company that you have provided to us
                  (consisting of a list of outstanding options to purchase the
                  Company's capital stock that was prepared by you and dated
                  August 21,1998 and a letter from the Company's transfer agent
                  dated August 21, 1998 certifying as to the number of
                  outstanding shares of Common Stock),


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HNC Software Inc.
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July 30, 1998


         (10)     a Management Certificate addressed to us and dated of even
                  date herewith executed by the Company containing certain
                  factual representations.

         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 legal capacity of all natural persons executing the same, 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 records
included in the documents referred to above. We have made no independent
investigation or other attempt 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.

         Our opinions herein are given on the assumption that the Company will,
at all times in the future, reserve a sufficient number of authorized and
unissued shares of its Common Stock for issuance under the HNC 1995 Plan, after
taking into account other securities issued or reserved by the Company.

         We are admitted to practice law in the State of California, and we
express no opinion herein with respect to the application or effect of the laws
of any jurisdiction other than the existing federal laws of the United States of
America and the internal laws of the State of California and (without reference
to case law or secondary sources) the existing Delaware General Corporation Law.

         Based upon the foregoing, it is our opinion that the 1,000,000
additional shares of Common Stock that may be issued and sold by the Company
upon the exercise of stock options, restricted stock purchases or stock bonuses
to be awarded under the HNC 1995 Plan, when issued and sold in accordance with
the HNC 1995 Plan and the stock option agreements, restricted stock purchase
agreements and stock bonus agreements to be entered into thereunder, and in the
manner referred to in the relevant Prospectus associated with the HNC 1995 Plan
and the Registration Statement, will be validly issued, fully paid and
non-assessable.

         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, the Prospectus constituting a part thereof and any
amendments thereto.

         This opinion speaks only as of its date and is intended solely for the
Company's use as an exhibit to the Registration Statement for the purpose of the
above issuance of securities referred to in the above opinion and is not to be
relied upon for any other purpose.

                                        Very truly yours,



                                        FENWICK & WEST LLP