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                                                                       Exhibit 5


                      [Letterhead of Dorsey & Whitney LLP]



                                September 7, 2001


Diametrics Medical, Inc.
2658 Patton Road
Roseville, MN 55113

     Re:  Registration Statement on Form S-8

Ladies and Gentlemen:

     We have acted as counsel to Diametrics Medical, Inc., a Minnesota
corporation (the "Company"), in connection with a Registration Statement on Form
S-8 relating to the sale by the Company from time to time of up to 900,000
shares of Common Stock, $.01 par value per share, of the Company ("the Shares"),
initially issuable pursuant to awards granted under the Company's 1990 Stock
Option Plan, 1993 Directors' Stock Option Plan and 1995 Employee Stock Purchase
Plan (the "Plans").

     We have examined such documents and have reviewed such questions of law as
we have considered necessary and appropriate for the purposes of the opinions
set forth below. We have assumed the authenticity of all documents submitted to
us as originals, the genuineness of all signatures and the conformity to
authentic originals of all documents submitted to us as copies. We have also
assumed the legal capacity for all purposes relevant hereto of all natural
persons. As to questions of fact material to our opinions, we have relied upon
certificates of officers of the Company and of public officials.

     Based on the foregoing, we are of the opinion that the Shares have been
duly authorized and, upon issuance, delivery and payment therefor in accordance
with the terms of the Plans, and any relevant agreements thereunder, will be
validly issued, fully paid and nonassessable.

     Our opinions expressed above are limited to the laws of the State of
Minnesota.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                       Very truly yours,


                                       /s/ Dorsey & Whitney LLP


KLC

