[PILLSBURY WINTHROP LLP LETTERHEAD]

                                                                     Exhibit 5.1


                                 July 26, 2001

Cardima, Inc.
47266 Benicia Street
Fremont, California 94538

Gentlemen:

     With reference to the Registration Statement on Form S-8 to be filed by
Cardima, Inc., a Delaware corporation (the "Company"), with the Securities and
Exchange Commission under the Securities Act of 1933, relating to 2,000,000
shares of the Company's Common Stock issuable pursuant to the Cardima, Inc. 1993
Stock Option Plan, as amended (the "Plan"), it is our opinion that such shares
of the Common Stock of the Company, when issued and sold in accordance with the
Plan, will be legally issued, fully paid and nonassessable.

     We hereby consent to the filing of this opinion with the Securities and
Exchange Commission as Exhibit 5.1 to the Registration Statement.

                         Very truly yours,

                         /s/ Pillsbury Winthrop LLP