EXHIBIT 5.1

                                 July 26, 2000

RITA Medical Systems, Inc.
967 North Shoreline Blvd.
Mountain View, CA 94043

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

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, Amendment No. 2 to the Registration Statement
filed on June 28, 2000, Amendment No. 3 to the Registration Statement filed on
July 14, 2000, Amendment No. 4 to the Registration Statement filed on July 19,
2000, Amendment No. 5 to the Registration Statement filed on July 24, 2000 and
Amendment No. 6 to the Registration Statement filed on July 25, 2000 (the
"Registration Statement") and a related registration statement that is
effective upon filing pursuant to Rule 462(b) under the Securities Act of 1933
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, 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