EXHIBIT 5.1

                               June 14, 2000

RITA Medical Systems, Inc.

967 North Shoreline Blvd.

Mountain View, CA 94043

   Registration Statement on Form S-1 (File No. 333-36160)

Ladies and Gentlemen:

   We have examined the Registration Statement on Form S-1 (File No. 333-36160)
(the "Registration Statement") filed by you with the Securities and Exchange
Commission on May 3, 2000, as amended by Amendment No. 1 to the Registration
Statement filed June 14, 2000 in connection with the registration under the
Securities Act of 1933 of shares of your Common Stock (the "Shares"). As your
legal counsel in connection with this transaction, we have examined the
proceedings taken and we are familiar with the proceedings proposed to be taken
by you in connection with the sale and issuance of the Shares.

   It is our opinion that upon conclusion of the proceedings being taken or
contemplated by us, as your counsel, to be taken prior to the issuance of the
Shares, and upon completion of the proceedings being taken in order to permit
such transactions to be carried out in accordance with the securities laws of
the various states where required, the Shares when issued and sold in the
manner described in the Registration Statement will be legally and validly
issued, fully paid and nonassessable.

   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.

                                          Very truly yours,

                                          VENTURE LAW GROUP

                                          A Professional Corporation

                                          /s/ Venture Law Group