[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 1,500,000
shares of the Company's Common Stock issuable pursuant to the Cardima, Inc. 1997
Employee Stock Purchase 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