Exhibit 5.1


                       [PILLSBURY WINTHROP LLP LETTERHEAD]


                                  June 22, 2001




Biosite Incorporated
11030 Roselle Street
San Diego, California 92121

Re: Registration Statement on Form S-8

Ladies and Gentlemen:

         With reference to the Registration Statement on Form S-8 to be filed by
Biosite Incorporated, a Delaware corporation (the "Company"), with the
Securities and Exchange Commission under the Securities Act of 1933, relating to
200,000 shares of the Company's Common Stock issuable pursuant to the Biosite
Incorporated Employee Stock Purchase Plan (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

                                                     PILLSBURY WINTHROP LLP