AGREEMENT

                   THIS  AGREEMENT is entered  into by and between  FRESENIUS AG
(AFresenius@) and GULL LABORATORIES, INC. ("Gull") on April ____, 1998.

                   WHEREAS,  Fresenius is the major  shareholder of Gull and the
current  employer  of Dr.  Silke  Humberg  ("Humberg").  Dr.  George  Evanega is
resigning as President and Chief Executive  Officer ("CEO") of Gull effective on
or about April 1, 1998; and

                   WHEREAS,  Gull  desires  to  employ  Humberg  as  its  acting
President and CEO, pending employment by Gull of a permanent  President and CEO;
and

                   WHEREAS,  the parties  recognize  that in order to obtain the
necessary  work permit and  governmental  authorization  for Humberg to commence
work for Gull on a timely basis, it will be necessary for Humberg to continue to
be employed and paid by Fresenius,  who will make Humberg available to Gull on a
full time basis,  subject to Gull=s  agreement  to reimburse  Fresenius  for the
costs of so doing.

                  NOW THEREFORE, the parties agree as follows:

                   1. Fresenius shall continue to employ Humberg  throughout the
term of this Agreement,  and shall make Humberg available to Gull on a full-time
basis to serve as acting president and CEO of Gull.

                   2.  Fresenius  shall pay all of  Humberg's  compensation  and
benefits,  which shall be as agreed upon by the board of  directors  of Gull and
Humberg.

                   3. At least  monthly,  Fresenius  shall  submit an invoice to
Gull for the direct  expenses  incurred by  Fresenius  in  compensating  Humberg
pursuant to this  Agreement.  Gull shall  reimburse  Fresenius  for the expenses
represented by the invoice within thirty (30) days of receipt of the invoice.

                   4. Either Fresenius or Gull may terminate this Agreement upon
thirty (30) days prior written notice to the other.

                   5. This Agreement shall not be deemed to create any rights in
Humberg or any other person not a party to this Agreement.

                   IN WITNESS WHEREOF, this Agreement has executed and delivered
by the parties as of the date first above written.

                                                      GULL LABORATORIES, INC.

                                                      By:
                                                      Title:

                                                      FRESENIUS AG

                                                      By:
                                                      Title: