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                                                                   EXHIBIT 10.34


                                 PROMISSORY NOTE


$100,000.00                                                       MAY 10 , 1999

     FOR VALUE RECEIVED, JAMES NELSON HARRIS, residing at 9890 Washingtonian
Blvd., Apt. 907, Gaithersburg, MD 20878 ("the "Borrower"), promises to pay to
the order of BioReliance Corporation (the "Corporation"), the principal sum of
ONE HUNDRED THOUSAND DOLLARS ($100,000) (the "Loan"), together with interest
thereon at the rate or rates hereafter specified and any and all other sums
which may be owing to the Corporation by the Borrower pursuant to the Promissory
Note (the "Note"). The following terms shall apply to this Note.

1.   Interest. For the period from the date of this Note through the fourth
     anniversary of the date of this Note (the "Maturity Date"), the unpaid
     principal balance outstanding from time to time pursuant to this Note shall
     bear interest at the rate of 5 1/2% percent per annum, compounded annually.

2.   Calculation of Interest. Interest shall be calculated on the basis of three
     hundred sixty (360) days per year factor applied to the actual days on
     which there exists an unpaid balance hereunder.

3.   Repayment. The Borrower shall pay any remaining principal balance, accrued
     and unpaid interest on the Maturity Date, on which date this Note shall
     mature, and the entire unpaid principal balance and accrued and unpaid
     interest thereon shall be due and payable; provided, however, that on each
     anniversary of the date hereof that the Borrower continues to be employed
     by the Corporation, $25,000 of the principal amount, together with interest
     accrued thereon, will be forgiven and the Borrower will not be obligated to
     pay such forgiven amount. The Borrower shall be responsible for any tax
     liability resulting from the forgiveness of any amount under this Note,
     including any withholding obligations on the part of the Corporation.

4.   Late Payment Charge. If any payment due hereunder is not received by the
     Corporation within 15 calendar days after its due date, the Borrower shall
     pay a late payment charge equal to five percent (5%) of the amount then
     due.

5.   Application of Payments. All payments made pursuant to this Note shall be
     applied first to accrued interest, then to principal, and then to late
     payments, charges or other sums owed to the Corporation, or in such other
     order or proportion as the Corporation, in the Corporation's sole
     discretion, may elect from time to time.

6.   Prepayment. The Borrower may prepay this Note in whole or in part at any
     time or from time to time without premium or penalty. The Corporation shall
     apply any


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     voluntary prepayment first to late charges and fees, then to accrued
     interest and default interest, and then to principal in the inverse order
     of scheduled maturities.

7.   Place of Payment. All payments due under this Note shall be made during
     regular business hours, without notice, to the Corporation, 14920 Broschart
     Road, Rockville, Maryland 20850, Attention: CFO, or to any other place that
     the Corporation may designate in writing, and shall be made in coin or
     currency of the United States of America which at the time of payment is
     legal tender for the payment of public or private debts.

8.   Default. The occurrence of any one or more of the following events shall
     constitute a default (a "Default") under the terms of this Note: (i) the
     failure of the Borrower to pay the Corporation when due any and all amounts
     payable by the Borrower to the Corporation under the terms of this Note; or
     (ii) the Borrower's employment with Corporation terminates prior to the
     fourth anniversary hereof (except for a termination by the Corporation
     without cause).

9.   Acceleration. Upon a Default, the Corporation, in the Corporation's sole
     and absolute discretion and without further notice or demand, may declare
     the entire unpaid principal balance of this Note (exclusive of forgiven
     amounts) plus accrued interest and all other sums due under this Note to be
     immediately due and payable and may exercise and all rights and remedies
     available under any of the Loan Documents.

10.  Confession of Judgment. Upon a Default, the Borrower authorizes the clerk
     or any attorney of any court of record to appear for it and enter judgment
     by confession without prior notice or opportunity for prior hearing for the
     principal balance then outstanding under this Note, together with interest,
     court costs and an attorney's fee equal to 15% of the sum of the principal
     balance then outstanding and interest then due hereunder, hereby waiving
     and releasing, to the extent permitted by law, all errors and all rights of
     exemption, appeal, stay of execution, inquisition, and extension upon any
     levy on real estate or personal property to which the Borrower may
     otherwise be entitled under the laws of the United States of America or of
     any state or possession of the United States of America now in force or
     which may hereafter be passed. The authority and power to appear for and
     enter judgment against the Borrower shall not be exhausted by one or more
     exercises thereof, or by any imperfect exercise thereof, and shall not be
     extinguished by any judgment entered pursuant thereto. Such authority and
     power may be exercised on one or more occasions, from time to time, in the
     same or different jurisdictions, as often as the Corporation shall deem
     necessary or desirable, for all of which this Note shall be a sufficient
     warrant.

11.  Consent to jurisdiction. The Borrower irrevocably submits to the
     jurisdiction of any state or federal court sitting in the State of Maryland
     over any suit, action, or proceeding arising out of, or relating to, this
     Note. The Borrower irrevocably waives, to the fullest extent permitted by
     law, any objection that the Borrower may now or hereafter have to the
     setting of venue of any suit, action, or proceeding brought in any



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     such court and any claim that any suit, action, or proceeding brought in
     any such court was brought in an inconvenient forum.

12.  Service of Process. The Borrower hereby consents to process being served in
     any suit, action, or proceeding instituted in connection with this Note by
     the mailing of a copy thereof by certified mail, postage prepaid, return
     receipt requested, to the Borrower at the following address 14920 Broschart
     Road, Rockville, Maryland 20850. The Borrower irrevocably agrees that the
     service specified herein shall be deemed to be service of process upon the
     Borrower in any suit, action, or proceeding. Nothing in this Note shall
     affect the Corporation's right to serve process in any other manner
     otherwise permitted by law.

13.  Notices. Any notice hereunder shall be deemed effective for all purposes as
     of the date the communication is mailed, postage prepared, be registered on
     certified mail, return receipt requested, to be delivered to address,
     addressed as follows:

      (i)    if to Borrower:

             9890 Washingtonian Blvd.
             Apt. 907
             Gaithersburg, MD  20878

      (ii)   if to Corporation:

             14920 Broschart Road
             Rockville, MD  20850
             Attention:  General Counsel

14.  Expenses of Collection. If this Note is referred to an attorney for
     collection after a Default, the Borrower shall pay all costs of collection,
     including attorneys' fees equal to 15% of the sum of the principal balance
     then outstanding and interest then due hereunder.

15.  Waiver of Protest. The Borrower waives presentment, notice of dishonor and
     protest.

16.  Choice of Law; Modifications; Cumulative Rights; Extensions of Maturity.

     (a)  No modification or amendment of this Note shall be effective unless in
          writing signed by the Corporation and the Borrower, and each
          modification or amendment, if any, shall apply only with respect to
          the specific instance involved.

     (b)  No waiver of any provision of this Note shall be deemed to be made by
          the Corporation unless in writing signed by the Corporation. Any
          waiver shall apply only with respect to the specific instance
          involved.



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     (c)  By accepting partial payment of any amount due and payable under this
          Note, the Corporation shall not be deemed to waive the right either to
          require prompt payment when due of all other amounts due and payable
          under this Note or to exercise any rights and remedies available to it
          in order to collect all other amounts due and payable under this Note.

     (d)  Each right, power and remedy of the Corporation hereunder or under
          applicable law shall be cumulative and concurrent and the exercise of
          any one or more of them shall not preclude the simultaneous or later
          exercise by the Corporation of any or all other rights, power, or
          remedies.

     (e)  No failure or delay by the Corporation to insist upon the strict
          performance of any one or more provisions of this Note or to exercise
          any right, power, or remedy consequent upon a breach thereof shall
          constitute a waiver thereof, or preclude the Corporation from
          exercising any such right, power or remedy.

17.  Illegality. In case any provision (or any part of any provision) contained
     in this Note shall for any reason be held to be invalid, illegal or
     unenforceable in any respect, such invalidity, illegality or
     unenforceability shall not affect any other provision (or remaining part of
     the affected provision) of this Note, but this Note shall be construed as
     if such invalid, illegal or unenforceable provision (or any part thereof)
     had never been contained herein, but only to the extent it is invalid,
     illegal or unenforceable.


                       [SIGNATURES APPEAR ON THE NEXT PAGE]


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     IN WITNESS WHEREOF, and intending to be legally bound hereby, the
undersigned executes this Note under seal as Borrower on the above written date.

WITNESS:                            BORROWER:

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

Name:                               /s/ James N. Harris                   (SEAL)
     ------------------             -------------------------------------
                                    Name:  James N. Harris
                                           ------------------------------------
                                    Title: Vice President, Sales and Marketing
                                           ------------------------------------



STATE OF MARYLAND, CITY/COUTY OF                                     , TO WIT:

      I HEREBY CERTIFY that on this_________ day of_________________________ ,
199__  , before me, a Notary Public in and for the State and City/County
aforesaid, personally appeared_____________, who acknowledge himself to be James
N. Harris, now or satisfactorily proven to me to be the person whose name is
subscribed to the within instrument, and acknowledged that he executed the same
for the purposes therein contained as its duly
authorized________________.

      AS WITNESS my hand and Notarial Seal.

                                    --------------------------------
                                    Notary Public


      My Commission expires:
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