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EXHIBIT 4.11

                               SUBORDINATION AGREEMENT



     This AGREEMENT entered into at Boston, Massachusetts, as of April 24, 1998,
between the undersigned holders of the 12% Senior Subordinated Debentures due
2005 of SeraCare, Inc. (each a "Creditor", and collectively, the "Creditors"),
and Brown Brothers Harriman & Co., a New York General Partnership with an
address of 40 Water Street, Boston, Massachusetts  02109 (the "Lender").


     For valuable consideration, receipt whereof is hereby acknowledged, and in
consideration of the loans, advances, discounts, renewals or extensions now or
hereafter made each by Lender to or for the account of SeraCare, Inc.
(hereinafter called the "Borrower"), each Creditor hereby agrees with the Lender
as follows:


     1.   Creditor represents to the Lender that the Borrower now owes Creditor
          the principal amount of $16,000,000, together with accrued and unpaid
          interest, fees and expenses (the "Debenture Indebtedness") and that
          the Debenture Indebtedness has not been assigned to or subordinated in
          favor of any other person or entity and that Creditor holds no
          security therefor. Creditor further represents that the Debenture
          Indebtedness is not represented by any notes or other negotiable
          instruments, except that certain 12% Senior Subordinated Debenture,
          dated February 13, 1998 (the "Debenture") by the Borrower in favor of
          the Creditor which contains a legend indicating that the Debenture is
          subordinate to the obligations owing by Borrower to Lender.  Creditor
          and, by its acknowledgment and agreement below, Borrower agree that if
          at any time the Debenture Indebtedness is evidenced by any notes,
          debentures, or instruments other than the Debenture, Creditor and
          Borrower shall cause such notes, debentures, or instruments to contain
          a legend substantially similar to the legend contained on the
          Debenture.


     2.   Creditor hereby subordinates all present and future indebtedness of
          the Borrower to Creditor (collectively, the "Pecks Indebtedness") to
          any and all indebtedness now or hereafter owing by the Borrower to the
          Lender (collectively, the "Lender Indebtedness") and agrees not to
          demand, accept or receive any payment of principal or interest upon
          account of the Pecks Indebtedness or any collateral therefor, until
          all Lender Indebtedness has been paid in full, except for regularly
          scheduled payments of principal and interest respecting the Pecks
          Indebtedness, provided there is no existing event of default
          continuing under Lender Indebtedness.  Creditor will not commence or
          join with any other creditor or creditors of Borrower in commencing
          any bankruptcy, reorganization or insolvency proceedings against
          Borrower.  Creditor also subordinates any claims that Creditor might
          assert against any guarantor of the Pecks Indebtedness to any and all
          claims assertable by the Lender against guarantors of the Lender
          Indebtedness. 


     3.   Subject to the Lender's priority of liens in the Lender's collateral
          securing the Lender Indebtedness, nothing in this Agreement shall
          prohibit Creditor from taking action (except to commence or join with
          any other creditor or creditors of Borrower in commencing any
          bankruptcy, reorganization or insolvency proceedings against Borrower)
          to enforce its rights under the Pecks Indebtedness after expiration of
          the Standstill Period (as hereinafter defined) so long as there is no
          existing uncured event of default involving the payment of money under
          the Pecks


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          Indebtedness.  "Standstill Period" shall mean the period of
          time commencing with the date on which Lender notifies Creditor that
          an event of default has occurred under the Lender Indebtedness,
          provided that such event of default has not been cured or waived, and
          expiring one hundred and eighty (180) days after the notice to Lender.
          If, during the Standstill Period, the default under the Lender
          Indebtedness is cured or waived, the Standstill Period shall cease
          running, and a new Standstill Period shall commence running when
          Lender gives notice that an additional event of default has occurred
          under the Lender Indebtedness.  The Standstill Period shall be tolled
          during any period of time that there is in effect an automatic stay
          under the Bankruptcy Code or an injunction or restraining order issued
          by a court prohibiting Lender from exercising its remedies, until a
          court of competent jurisdiction has lifted such stay, injunction, or
          restraint.


     4.   Subject to the terms of paragraph 2 of this Agreement, should any
          payment be received by Creditor for or on account of any of the Pecks
          Indebtedness, prior to the satisfaction of all Lender Indebtedness,
          Creditor will forthwith deliver the same to the Lender, in precisely
          the form received (except for Creditor's endorsement where necessary)
          for application on account of the Borrower's obligations to the Lender
          and, until so delivered, the same shall be held in trust by Creditor
          as the property of the Lender.


     5.   In order to carry out the terms and the intent of this agreement more
          effectively, Creditor will do all acts and execute all further
          instruments reasonably requested by the Lender as necessary or
          convenient to preserve for the Lender the benefit of this
          Subordination Agreement.


     6.   Creditor further waives presentment, notice and protest in connection
          with all negotiable instruments evidencing the indebtedness
          subordinated hereby or Borrower's indebtedness to Lender, notice of
          the acceptance of this agreement by Lender, notice of any loan made,
          extension granted or other action taken in reliance hereon and all
          demands and notices of every kind in connection with this agreement,
          or the indebtedness of Borrower to Lender or to Creditor; assents to
          any renewal, extension or postponement of the time of payment of the
          Lender Indebtedness or any other indulgence with respect thereto, to
          any substitution, exchange or release of collateral therefor and to
          the addition or release of any person primarily or secondarily liable
          thereon; and agrees to the provisions of any instrument, security or
          other writing evidencing the Lender Indebtedness.  No action which the
          Lender, or the Borrower with the consent of the Lender, may take or
          refrain from taking with respect to any Lender Indebtedness, or any
          note or notes representing the same, or any collateral therefor,
          including a waiver or release thereof or any agreement or agreements
          (including guaranties) in connection therewith, shall affect this
          agreement or the obligations of Creditor hereunder.  If all Lender
          Indebtedness is at any time hereafter paid in full and thereafter
          Borrower again becomes indebted to the Lender, the provisions of this
          agreement shall apply to said new indebtedness unless, before the same
          is incurred, Creditor notifies the Lender in writing of the
          cancellation of this agreement.


     7.   No waiver shall be deemed to be made by Lender of any of its rights
          hereunder unless the same shall be in writing and shall be a waiver
          only with respect to the specific instance involved unless otherwise
          provided for in such waiver; and it shall in no way impair Lender's
          rights or Creditor's obligations to it in any other respect or any
          other time.  This Subordination Agreement incorporates all discussions
          and negotiations between Creditor and Lender concerning the
          subordination provided by Creditor hereby, and no such discussions or
          negotiations shall limit, modify or otherwise affect the provisions
          hereof, and no provision hereof may be altered, amended, waived,
          canceled or modified, except by a written instrument executed and
          delivered by a duly authorized officer of Lender.


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     8.   The rights granted to the Lender hereunder are solely for its
          protection and nothing herein contained shall impose on the Lender any
          duties with respect to any property of the Borrower or Creditor
          received hereunder, beyond reasonable care in its custody and
          preservation while in the Lender's possession.  The Lender shall have
          no duty to preserve rights against prior parties in any instrument or
          chattel paper received hereunder or pursuant to this agreement.


     9.   In the event of a conflict between the terms of this Agreement and the
          terms of Section 8 of that certain Securities Purchase Agreement,
          dated as of February 13, 1998, among Borrower, Avre, Inc., Binary
          Associates, Inc., BHM Labs, Inc., SeraCare Acquisitions, Inc.,
          SeraCare Technology, Inc., and the Creditors, the terms of this
          Agreement shall govern.  This agreement shall bind Creditor and
          Creditor's heirs, successors, assigns and legal representatives and
          shall inure to the benefit of the Lender and its successors and
          assigns, and shall be governed by and construed in conformity with the
          laws of the Commonwealth of Massachusetts.


          EXECUTED under seal as of the date first above written.

Witness                                Creditors:

                                       DECLARATION OF TRUST
                                       FOR DEFINED BENEFIT PLANS
                                       OF ZENECA HOLDINGS INC.


                                       DECLARATION OF TRUST
                                       FOR DEFINED BENEFIT PLANS
                                       OF ICI AMERICAN HOLDINGS INC.

                                       DELAWARE STATE EMPLOYEES'
                                       RETIREMENT FUND

                                       THE J. W. MCCONNELL FAMILY
                                       FOUNDATION

                                       By:  Pecks Management Partners Ltd.,
                                       Its Investment Advisor
           
-----------------------------          By:        /s/ Robert J. Cresci
                                          -------------------------------------
                                          Robert J. Cresci, General Partner
           
           



ACCEPTED:  BROWN BROTHERS HARRIMAN & CO.

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

          
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     The Borrower above named hereby acknowledges notice of the within and
foregoing subordination and agrees to be bound by all the terms, provisions and
conditions thereof.
     
     
Witness                                Borrower:
                                       

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



     
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