April 20, 2000

VIA FED EX

Robert A. Baffi, Ph.D.
8 Elston Court
San Carlos, CA  94070


Dear Robert:

         I am pleased to offer you the  position  of Vice  President  of Quality
Assurance  and  Quality  Control at  BioMarin  Pharmaceutical  Inc. At the Board
meeting of April 19th, you were named an executive officer of BioMarin. You will
report directly to Bill Anderson, our Chief Financial Officer and Vice President
of Finance and Administration. You will be responsible for directing the quality
operations  (internal and external) of all BioMarin and Joint Venture  products;
manage  quality  operations  for clinical  and  commercial  requirements  in all
BioMarin  facilities,  including Bel Marin Keys and Galli Drive, Phases 1 and 2;
quality  control,  quality  assurance and validation  activities;  contribute to
quality  participation in efficient process  development and process changes for
cost  effective  manufacture;  responsible  for  budgets,  forecasts  and actual
financial performance of the Quality organization; and other duties as required.

         Your starting salary at BioMarin will be $200,000 per year. As you will
note from the attached addendum, BioMarin will pay some of your moving expenses.
Although an annual performance bonus cannot be guaranteed at this time, BioMarin
did award short term incentive  compensation for 1999 performance which was paid
in stock  options  at the end of 1999.  We  anticipate  a  continuation  of this
program at the end of 2000 with the likelihood that the means of payment will be
stock options.  You would be a participant  in 2000 awards on a pro-rated  basis
for time with the Company during 2000.

         As additional incentive, the BioMarin Board of Directors has granted to
you stock  options  to  purchase  200,000  shares of  common  stock in  BioMarin
Pharmaceutical Inc. The exercise price of these stock options will be determined
by the Nasdaq closing price on your first day of employment with BioMarin. These
stock  options will have a vesting  schedule as follows:  15% will vest upon FDA
approval of PAI and 15% will vest upon the filing of the BLA of Aldurazyme.  The
above 30% will vest in any case upon the  completion  of four  years of  service
after your start date. The remaining 70% of your





Robert A. Baffi, Ph.D.
Page 2
April 20, 2000


options  shall vest as follows:  6/48ths  upon the  completion  of six months of
employment and 1/48 per month thereafter.

         You will  receive  an  additional  10,000  shares  of  common  stock in
BioMarin  Pharmaceutical  Inc. The exercise price of these stock options will be
determined  by the Nasdaq  closing  price on your first day of  employment  with
BioMarin.  These stock  options  will have a vesting  schedule  as follows:  50%
vesting after six months of employment  and monthly  vesting  thereafter at 1/12
per month.  You will be fully vested in those options one year from grant.  Both
sets of options  will  expire  ten years  after the date of grant.  Should  your
employment  with the company  terminate for any reason your vested stock options
will expire 90 days beyond your termination  date, if not previously  exercised.
Unvested options will immediately cease to vest.

         Upon a change of  control,  should such an event  occur,  you will have
essentially  the same agreement terms as other officers which are detailed in an
attachment  to this  letter.  You will  also be  subject  to an  indemnification
agreement  which  includes   essentially  the  same  terms  as   indemnification
agreements with other officers and directors.

         As a regular  employee at BioMarin you will accrue three weeks per year
of paid vacation and be eligible to be covered by the company's medical, dental,
and group life insurance  plans. A description of the company's  employee manual
was previously  sent to you and you acknowledge  receipt of that  information by
your signature below.

         Your employment may be terminated at any time by BioMarin without cause
upon  six  months'  notice  to you  and by you  upon  three  months'  notice  to
BioMarin's  Board of  Directors.  If your  employment  is  terminated  under the
provisions of this  paragraph,  BioMarin shall  determine in its sole discretion
whether you shall continue to discharge your duties as Vice President of Quality
Assurance  and  Quality  Control.   In  any  case,  you  shall  be  entitled  to
compensation and benefits as provided in this letter until the effective date of
your termination.

         If, within twelve months of this letter, your employment terminates for
"cause" (as defined  herein),  you shall not be  entitled  to  compensation  and
benefits  as  provided  in this  letter.  "Cause"  is  defined  as (i) an act of
personal dishonesty taken by you in connection with your  responsibilities as an
employee  and  intended  to  result  in  your  personal  enrichment,  (ii)  your
conviction or, plea of nolo contendere to, a felony,  (iii) a willful act by you
which  constitutes  gross misconduct and which is injurious to the Company,  and
(iv)  following  delivery to you of a written  demand for  performance  from the
Company which describes the basis for the Company's belief that you have not





Robert A. Baffi, Ph.D.
Page 3
April 20, 2000


substantially  performed  your  duties,  continued  violations  by you  of  your
obligations to the Company.  The notice of  termination  under the provisions of
this paragraph  shall state the grounds for  termination  and state all relevant
facts supporting the grounds.

         If you, in the opinion of a licensed medical doctor, become mentally or
physically  incapacitated  to the extent that you are unable to  discharge  your
employment duties for a period of six months or more, BioMarin shall continue to
provide you, for a period ending six months from the determination of incapacity
with the  compensation as set out in this letter.  If you die during the term of
your  employment,  BioMarin shall continue to pay, for six months following your
death, your  compensation,  as set out in this letter, to your surviving spouse,
if there is one, or if not, to the executor or administrator to your estate.

         This offer of employment is made contingent on your providing  BioMarin
with the legally  required proof of your identity and  authorization  for you to
work in the  United  States.  Please be  advised  that  nothing in this offer is
intended to imply an employment contract of specific duration with BioMarin.

         We are all  eagerly  looking  forward to working  with you. As you know
this is an exciting time in BioMarin's  early growth and I believe you will find
this a very challenging and rewarding experience.  If you accept this offer, you
can plan on starting on or before May 9, 2000.

Sincerely,



R. W. Anderson
Vice President of Finance and Administration
Chief Financial Officer

I accept this offer


-------------------


Date: ______________





                               RELOCATION ADDENDUM

         BioMarin  will pay  your  moving  and  relocation  expenses,  up to and
including,  Fifty Thousand  Dollars  ($50,000.00)  as indicated  below.  We will
reimburse you from your receipts.

         BioMarin  must  follow  the IRS  guidelines  as to  taxable/non-taxable
status for relocation reimbursement by an employer. Reimbursement for relocation
expenses  received from BioMarin will not be considered income for expenses that
would be  deductible as a moving  expense if directly paid by the employee.  Any
amount paid by BioMarin that would not be  considered a qualified  reimbursement
for relocation expenses will be included as gross income and taxed.

         Deductible   moving   expenses   are   limited   to  the  cost  of  (1)
transportation of household goods and personal effects and (2) travel (including
lodging but not meals) to the new residence.

         To be eligible for the moving  expense a distance test must be met. The
new  principal  place  of work  must be at  least  50  miles  farther  from  the
taxpayer's  old residence  than the old residence  was from the  taxpayer's  old
place of work.

         Where an  automobile  is used in making the move, a taxpayer may deduct
either (1) the actual out-of-pocket expenses incurred (gasoline and oil, but not
repairs,  depreciation,  etc.) or (2) a standard mileage  allowance of ten cents
per mile.

         Any additional relocation expense that you incur that is not deductible
will be paid by BioMarin but will be taxed per the IRS. Those additional  monies
will  show  up  as  gross  income.  If  you  need  clarification  or  additional
information, please consult your tax advisor.

-------------------------------
R. W. Anderson
Vice President, Finance and Administration
Chief Financial Officer

-------------------------------
Robert Baffi

Date:  __________________________