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                                                                EXHIBIT 5.1


                 [WILSON SONSINI GOODRICH & ROSATI LETTERHEAD]



Calypte Biomedical Corporation
1440 Fourth Street
Berkeley, CA 94710


        RE: REGISTRATION STATEMENT ON FORM S-1
            (COMMISSION FILE NO. 333-4105)

Ladies and Gentlemen:

        We have examined the Registration Statement on Form S-1 to be filed with
the Securities and Exchange Commission (the "Registration Statement"), in
connection with the registration under the Securities Act of 1993, as amended,
of 2,875,000 shares (including an over-allotment option granted by the Company
to the underwriters to purchase 375,000 shares) of your Common Stock (the
"Shares"), all of which are authorized. The Shares are to be sold to the
underwriters for resale to the public as described in the Registration Statement
and pursuant to the Underwriting Agreement being filed as an exhibit thereto.
As your counsel, we have examined the proceedings proposed to be taken in
connection with the sale and issuance of the Shares.

        It is our opinion that, upon completion 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 referred to 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 any amendment thereto.

                                        Very truly yours,

                                        
                                        WILSON SONSINI GOODRICH & ROSATI
                                        Professional Corporation

                                        /s/ Wilson Sonsini Goodrich & Rosati