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                                                                     EXHIBIT 5.1


                                 HELEN W. MELMAN
                                 Attorney at Law
                                815 Moraga Drive
                          Los Angeles, California 90049
                            Telephone (310) 472-4191
                            Facsimile (310) 472-4091


                                                                    May 11, 2001

Diagnostic Products Corporation
5700 West 96th Street
Los Angeles, CA 90045


         Re:      Registration Statement on Form S-8
                  ----------------------------------

Gentlemen:

     Diagnostic Products Corporation, a California corporation (the "Company"),
proposes to issue and sell up to 1,000,000 shares of its Common Stock, no par
value (the "Shares"), upon the exercise of stock options granted and to be
granted from time to time under the Company's 1997 Stock Option Plan, as amended
through the date hereof (the "Plan"). The Shares are being registered on a
Registration Statement on Form S-8 under the Securities Act of 1933, as amended
(the "Act"), to be filed with the Securities and Exchange Commission on or about
May 11, 2001.

     In connection with rendering the opinion hereinafter expressed, I have
examined originals, certified copies or other copies identified to my
satisfaction of the following documents and instruments:

     1.   Articles of Incorporation of the Company, as amended to date;

     2.   Bylaws of the Company, as amended to date;

     3.   Certain minutes of meetings of the Board Directors and Shareholders of
          the Company;

     4.   The Plan;

     5.   The Registration Statement, together with the exhibits to be filed in
          connection therewith, in the form to be filed with the Commission; and


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Diagnostic Products Corporation
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     6.   The documents to be delivered to the holders of stock options which
          will constitute the prospectus under Section 10(a) of the Act.

     I have obtained from public officials and from officers of the Company and
examined originals or copies, identified to my satisfaction, of such other
certificates, agreements and other assurances as I consider necessary for the
purpose of rendering the opinion hereinafter expressed.

     I have additionally consulted with officers and representatives of the
Company and have obtained such representations with respect to matters of fact
as I deem necessary or advisable. I have not necessarily independently verified
the content of the factual statements made to me in connection therewith, nor
the veracity of such representations, but I have no reason to doubt their truth
or accuracy.

     Based on the foregoing, it is my opinion that the Shares, when issued, sold
and paid for in accordance with the terms of the Plan, will be duly and validly
issued, fully paid and non-assessable.

     I hereby consent to this opinion being filed as an exhibit to the
Registration Statement. In giving this consent, I do not admit that I am in the
category of persons whose consent is required under Section 7 of the Act or the
rules and regulations of the Commission thereunder.



                                               Very truly yours,



                                               /S/ HELEN W. MELMAN

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