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                                                                   Exhibit 10.81

                        [Calypte Biomedical Letterhead]


October 31, 2000



Dr. Howard B. Urnovitz
Chronix Biomedical Corporation
755 Tennesee Street #3
San Francisco, CA  94107

Dear Howard:

The purpose of this letter is to amend certain provisions of your January 1,
1995 employment agreement, as amended on November 17,1999. These amendments are
necessary as a result of your recent decision to activate Chronix Biomedical and
to devote a considerable portion of your time to the building of that
non-competitive business. Notwithstanding this development, both you and we wish
you to continue in your role as Chief Scientific Officer for Calypte Biomedical.
To these ends, we have agreed as follows:

1.)      Section 2 is amended to read as follows:
         For the period April 1, 2000 to March 31, 2001, Executive shall
         serve as Chief Scientific Officer with the following
         responsibilities:
         a.)      Active participation on the Technical Committee of the Board,
                  including participation in the meetings either in person or by
                  phone;
         b.)      Consultation on request with Toby Gottfried and other members
                  of the Company's scientific staff and consultants on
                  scientific matters of importance to our business of
                  diagnostics;
         c.)      Support for the Company's business by working to maintain good
                  relations for the Company with individuals and institutions
                  important to Calypte's success with whom you have had close
                  relationships in the past and per your approval. Examples
                  would include Dr. Luc Montagnier, Dr. Alvin Friedman-Kien,
                  Otsuka Pharmaceutical, and various members of the
                  congressional, scientific and AIDS community. This may involve
                  some travel which would be at your convenience and Calypte's
                  expense.
         d.)      Undertake to keep the Technical Committee and the Board
                  informed of any of your activities or the activities of others
                  which come to your attention and which in your judgment might
                  have important bearing on our urine-based diagnostics
                  business.

2.)      Section 1 is amended to read as follows:
         Executive shall receive as compensation an amount equal to $50,000
         cash for the period April 1, 2000 to October 31, 2000. For the
         period November 1, 2000 to March 31, 2001, Executive will receive
         $50,000 in Calypte's common stock issuable as on December 1, 2000.
         The price per share at which the stock shall be issued shall be the
         closing price on any day selected by the Executive between the
         signing date of this amendment and November 30, 2000 or on November
         30, 2000 if no selection is made.
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         In light of his employment relationship with Chronix Biomedical,
         Executive shall not be eligible for the various Calypte Biomedical
         employee benefit plans, including the medical plan and the 401k plan.

3.)      Section 3 is amended to read as follows:
         Executive shall be entitled to reimbursement for those out-of-pocket
         business expenses related to the business affairs of Calypte.

4.)      Section 8 (c) is amended to read as follows:
         The Executive or the Company may terminate this agreement at any time
         and for any or no reason, upon two (2) weeks prior written notice to
         the other party. Termination shall not affect prior compensation paid.

Howard, except as specifically modified hereby, your 1995 employment agreement,
amended in 1999, remains in effect. I trust the above reflects accurately our
recent discussions. If so, please sign and return one copy of this letter to me
at the Alameda office.

Sincerely,

/s/ NANCY E. KATZ

Nancy E. Katz
President and CEO





Agreed:



/s/ HOWARD B. URNOVITZ
--------------------------------
Howard B. Urnovitz

Date signed:  November 2, 2000