[LETTER HEAD]

                                     EXHIBIT 5.1

                                  November 4, 1997

SuperGen, Inc.
Two Annabel Lane, Suite 220
San Ramon, CA  94583

    RE:  REGISTRATION STATEMENT ON FORM S-8

Ladies and Gentlemen:

    We have examined the Registration Statement on Form S-8 filed by you with
the Securities and Exchange Commission on July 1, 1996 and Post-Effective
Amendment No. 1 thereto to be filed by you on or about November 4, 1997 (the
"Registration Statement"), in connection with the registration under the
Securities Act of 1933, as amended, of (i) 2,500,000 shares of your Common Stock
reserved for issuance under the 1993 Stock Option Plan, as amended and restated
effective February 3, 1996 (the "1993 Plan"), (ii) 250,000 shares of your Common
Stock reserved for issuance under the 1996 Directors' Stock Option Plan (the
"1996 Plan"), as amended effective February 3, 1997, and (iii) 300,000 shares of
your Common Stock reserved for issuance under the Employees and Consultants
Stock Option Agreement/Plan (the "Employees and Consultants Plan").   The
2,500,000 shares of Common Stock reserved under the 1993 Plan, the 250,000
shares of Common Stock reserved under the 1996 Plan and the 300,000 shares of
Common Stock reserved under the Employees and Consultants Plan are referred to
collectively as the "Shares," and the 1993 Plan, the 1996 Plan and the Employees
and Consultants Plan are referred to collectively as the "Plans."  As your legal
counsel, we have examined the proceedings taken and proposed to be taken in
connection with the issuance, sale and payment of consideration for the Shares
to be issued under the Plans.

    It is our opinion that, when issued and sold in compliance with applicable
prospectus delivery requirements and in the manner referred to in the Plans and
pursuant to the agreements which accompany the Plans, the Shares 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 and any amendments thereto.

                             Sincerely,

                             WILSON, SONSINI, GOODRICH & ROSATI
                             Professional Corporation
                             
                             /S/ WILSON, SONSINI, GOODRICH & ROSATI