EXHIBIT 5.1

                                Venture Law Group
                           A Professional Corporation
                               2775 Sand Hill Road
                              Menlo Park, CA 94025

April 30, 2003

Persistence Software, Inc.
1720 South Amphlett Blvd., Third Floor
San Mateo, California 94402

REGISTRATION STATEMENT ON FORM S-3
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Ladies and Gentlemen:

         We have examined the Registration Statement on Form S-3 (the
"REGISTRATION STATEMENT") filed by you with the Securities and Exchange
Commission (the "COMMISSION") on or about April 30, 2003 in connection with the
registration under the Securities Act of 1933, as amended, of 3,758,692 shares
of your currently issued and outstanding common stock (the "SHARES"), sold to
certain stockholders, and 1,335,130 shares of your common stock (the "WARRANT
SHARES") issuable upon exercise of warrants issued to certain stockholders (the
"WARRANTS"), in each case as listed in the Registration Statement (the "SELLING
STOCKHOLDERS"). As your legal counsel in connection with this transaction, we
have examined the proceedings taken and are familiar with the proceedings taken
by you in connection with the sale and issuance of the Shares.

         It is our opinion that the Shares are legally and validly issued, fully
paid and non-assessable, and that the Warrant Shares, when issued on exercise of
the Warrants and in accordance with their terms, will be legally and 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 the use of our name wherever appearing in the
Registration Statement, including the prospectus constituting a part thereof,
and in any amendment thereto.


                                                       Sincerely,

                                                       /S/ VENTURE LAW GROUP
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LF