EXHIBIT 5.1


                          PILLSBURY MADISON & SUTRO LLP
                              235 Montgomery Street
                             San Francisco, CA 94104
                               Tel: (415) 983-1000


                                                     February 26, 1998




Heska Corporation
1825 Sharp Point Drive
Fort Collins, CO 80525


         Re:   Registration Statement on Form S-8


Gentlemen:

         With reference to the Registration Statement on Form S-8 to be filed by
Heska Corporation, a Delaware corporation (the "Company"), with the Securities
and Exchange Commission under the Securities Act of 1933, as amended, relating
to 942,701 shares of the Company's Common Stock issuable pursuant to the
Company's 1997 Stock Incentive Plan (the "Stock Plan"), it is our opinion that
such shares of the Common Stock of the Company, when issued and sold in
accordance with the Stock 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 MADISON & SUTRO LLP




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