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EXHIBIT 4.12

                      A.   BORROWING AND AGENCY AGREEMENT

                                                                 April 24, 1998



Brown Brothers Harriman & Co.

40 Water Street, Boston

Massachusetts  02109 




Gentlemen:




     The undersigned, SeraCare, Inc., a California Corporation, with an 
address of 1925 Century Park East, Suite 1970, Los Angeles, California 90067 
("SeraCare"), Avre, Inc., a Nevada corporation, with an address of 3529 W. 
McDowell, Phoenix, Arizona 85029 ("Avre"); Binary Associates, Inc., a 
Colorado corporation with an address of 1925 Century Park East, Suite 1970, 
Los Angeles, California 90067("Binary"); SeraCare Acquisitions, Inc., a 
Nevada corporation, with an address of 1925 Century Park East, Suite 1970, 
Los Angeles, California 90067 ("Acquisitions"); BHM Labs, Inc., an Arkansas 
corporation, with an address of 910 N. 32nd Street, Fort Smith, Arizona 85029 
("BHM"); Sera Care Technology, Inc., a Nevada corporation, with an address of 
2170 Woodward, Austin, Texas 78744 ("Technology"); Western States Group, 
Inc., a California corporation, with an address of 131 W. Beech Street, Suite 
A, Fallbrook, California 92028 are referred to as the "PRINCIPAL OBLIGORS" 
and SeraCare, is referred to in such additional capacity as the "AGENT 
BORROWER", have requested that you establish certain loan arrangements with 
them (hereinafter the "Loan Arrangements"), and are today executing a 
Revolving Loan and Security Agreement, Revolving Term Note and other 
documents with Brown Brothers Harriman & Co. (hereinafter the "Lender"), 
pursuant to which the Lender will make revolving credit loans, or otherwise 
extend credit accommodations to the Principal Obligors, subject to the terms 
and conditions therein set forth.  

     The undersigned request that as a convenience to them, such loans as may 
be 


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made under the Loan Arrangement be directed to the Agent Borrower which will, 
in turn, distribute the proceeds thereof to the Principal Obligors.  As an 
additional inducement for Lender to establish the Loan Arrangements and to 
direct such loans as may be made thereunder to the Agent Borrower, as 
described above, each of the undersigned covenants and agrees as follows:

     1.   Loans and advances under the Loan Arrangement shall be requested 
solely by the Agent Borrower as agent for the Principal Obligors.  In 
connection therewith each Principal Obligor has authorized the Agent Borrower 
to execute promissory notes to the Lender from time to time to evidence the 
liabilities, obligations and indebtedness of the Principal Obligors to the 
Lender.  The authority of the Agent Borrower so to request loans on behalf 
of, and to bind, the Principal Obligors, shall continue unless and until 
Lender actually receives written notice of the termination of such authority, 
which notice is signed by the respective Presidents or Treasurers of each of 
the Principal Obligors.

     2.   Any advances which may be made by Lender under the Loan 
Arrangements which are directed to the Agent Borrower shall be received by 
the Agent Borrower in trust for the Principal Obligors.  The Agent Borrower 
shall distribute the proceeds of any such advances solely to the Principal 
Obligors for such uses as are permitted under the Loan Arrangements.  Each 
Principal Obligor shall be directly indebted to Lender for each advance 
distributed to it by the Agent Borrower as if that amount had been advanced 
directly by Lender to the Principal Obligor which received such proceeds.  In 
addition, the other Principal Obligors shall also be obligated to Lender in 
such amount.

     3.   All advances by Lender to and for each Principal Obligor made 
directly to the Agent Borrower under the Loan Agreement shall be based on the 
collective Borrowing Base of all Principal Obligors pursuant to the terms of 
such Loan Arrangement.  

     4.   All notices to be made by Lender to all Principal Obligors shall be 
deemed duly given if they are in writing and addressed to the Agent Borrower 
at its address as set forth in the Loan Arrangements, or at any other place 
such party may designate by notice in writing in accordance therewith.

     5.   The Lender shall have no responsibility to inquire as to the 
distribution of loans and advances made by Lender through the Agent Borrower 
as described herein.  The Agent Borrower and each of the Principal Obligors 
agrees to indemnify, defend, and to hold Lender harmless of, to, and from any 
liability, claim, demand, expense, or loss made against Lender on account of, 
or arising out of, the Loan Arrangements, and the Lender's reliance upon loan 
requests made by the Agent Borrower.

     6.   The Lender may issue one monthly statement to the Agent Borrower on 
behalf of all of the Principal Obligors, which statement shall cover all of 
the loans and advances made by Lender through the Agent Borrower as described 
herein and shall be deemed correct and accepted by the Agent Borrower and 
each of the Principal Obligors, unless Lender is 


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provided within fifteen (15) days of the receipt of that statement by Agent 
Borrower with written notice by the Agent Borrower of exceptions with respect 
to that monthly statement.  Such notice shall set forth, with reasonable 
particularity, the reasons for such exceptions.

     7.   In consideration of the continuance of the mutually beneficial 
business relationships of the Principal Obligors, and to induce the Lender to 
enter into the Loan Arrangements, each of the Principal Obligors hereby 
agrees to guarantee the payment when due of the other Principal Obligors' 
indebtedness to the Lender from time to time outstanding in accordance with 
the terms of that certain Cross-Guaranty Agreement, of even date herewith, by 
the Principal Obligors in favor of the Lender.

     8.   If any term or provision of this Agreement, or the application 
thereof to any person or circumstance, shall to any extent be invalid or 
unenforceable, the remainder of this Agreement, or the application of such 
terms or provisions to persons or circumstances other than those as to which 
it is invalid or unenforceable, shall not be affected thereby, and each term 
and provisions of this Agreement shall be valid and be enforced to the 
fullest extent permitted by law.

                                          
                             [INTENTIONALLY LEFT BLANK]


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                                     Very truly yours,


                                     PRINCIPAL OBLIGORS:


                                     SeraCare, Inc.



----------------------               By:   /s/ Barry D. Plost
                                         --------------------------------
                                         Barry D. Plost, Chairman and CEO



                                     Avre, Inc. 



----------------------               By:   /s/ Barry D. Plost
                                         --------------------------------
                                         Barry D. Plost, Chairman and CEO



                                     Binary Associates, Inc.



----------------------               By:   /s/ Barry D. Plost
                                         ------------------------------------
                                         Barry D. Plost, Chairman and CEO



                                     SeraCare Acquisitions, Inc.



----------------------               By:   /s/ Barry D. Plost
                                         ------------------------------------
                                         Barry D. Plost, Chairman and CEO



                                     BHM Labs, Inc.



----------------------               By:   /s/ Barry D. Plost
                                         ------------------------------------
                                         Barry D. Plost, Chairman and CEO


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                                     SeraCare Technology, Inc.



----------------------               By:   /s/ Barry D. Plost
                                         ------------------------------------
                                         Barry D. Plost, Chairman and CEO


                                     Western States Group, Inc.


----------------------               By:   /s/ Barry D. Plost
                                         ------------------------------------
                                         Barry D. Plost, Chairman and CEO
                                   
                                   
                                   
                                   
                                   AGENT BORROWER


                                     SeraCare, Inc.



                                     By:   /s/ Barry D. Plost
                                         ------------------------------------
                                         Barry D. Plost, Chairman and CEO

Accepted: Brown Brothers Harriman & Co.



By:    /s/ Joseph E. Hall
   --------------------------------
     Joseph E. Hall, Deputy Manager








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