Exhibit 5.1

                                January 11, 2001

BioMarin Pharmaceutical Inc.
371 Bel Marin Keys Boulevard, Suite 210
Novato, CA 94949

         Re:      Registration Statement on Form S-3

Ladies and Gentlemen

     You  have  requested  our  opinion  with  respect  to  certain  matters  in
connection  with  the  filing  by  BioMarin   Pharmaceutical  Inc.,  a  Delaware
corporation  (the  "Company")  of a  Registration  Statement  on Form  S-3  (the
"Registration Statement") with the Securities and Exchange Commission, including
a prospectus (the "Prospectus")  covering the offering of a maximum of 4,000,000
shares of the  Company's  Common  Stock,  $0.001  par value ( the  "Shares")  as
described in the Registration Statement.

     In  connection  with this  opinion,  we have  examined  and relied upon the
Registration  Statement  and  related  Prospectus,  the  Company's  Amended  and
Restated  Certificate of Incorporation,  the Company's  Restated Bylaws, and the
originals or copies  certified to our  satisfaction of such documents,  records,
certificates,  memoranda and other  instruments as in our judgment are necessary
or  appropriate  to enable us to render the  opinion  expressed  below.  We have
assumed the  genuineness and  authenticity  of all documents  submitted to us as
copies  thereof,  and the due execution and delivery of all documents  where due
execution and delivery are a prerequisite to the effectiveness thereof, and that
at the time the Shares are issued,  the Company will have sufficient  authorized
and unissued shares of Common Stock, that the terms of the offer and sale of the
Shares will have been properly  authorized by resolutions of the Company's Board
of Directors and that such resolutions  shall require,  among other things,  the
payment of valid consideration for the Shares.

     On the  basis of the  foregoing,  and in  reliance  thereon,  we are of the
opinion  that the  Shares,  when  issued  and paid  for in  accordance  with the
Registration  Statement and  authorizing  resolutions of the Company's  Board of
Directors, will be legally issued, fully paid, and nonassessable.

     We  hereby  consent  to  being  named  as  counsel  to the  Company  in the
Registration  Statement, to the references therein to our firm under the caption
"Legal  Matters"  and to the  inclusion  of this  opinion  as an  exhibit to the
Registration  Statement.  This opinion is rendered to you in connection with the
Registration  Statement and is solely for your benefit.  This opinion may not be
relied upon by you for any other  purpose,  or relied upon by any other  person,
firm or other entity for any purpose, without our prior written consent.

                                Very truly yours,

                    /s/ Paul, Hastings, Janofsky & Walker LLP

                      PAUL, HASTINGS, JANOFSKY & WALKER LLP