

                                 PROMISSORY NOTE


         U.S. 187,000,000                             New York, New York
                                                    December 30, 1996


          FOR VALUE RECEIVED, LABORATORY CORPORATION OF AMERICA
     HOLDINGS, a Delaware corporation (the "Borrower"), by this
     Promissory Note hereby unconditionally promises to pay no later
     than March 31, 1997 (the "Maturity Date"), to the order and for
     the account of ROCHE HOLDINGS INC. (the "Lender") at a bank to be
     designated by the Lender by notice to the Borrower, the principal
     amount of ONE HUNDRED AND EIGHTY SEVEN MILLION DOLLARS in lawful
     money of the United States of America in same day funds.
     
          The Borrower shall pay interest in like funds on the unpaid
     principal amount hereof until the unpaid principal amount under
     this Note is paid in full.  Interest shall accrue from the date
     hereof on the outstanding principal amount of this Note at a rate
     per annum equal to 6.625%. Interest shall be calculated on the
     basis of a year of 360 days and the actual number of days elapsed
     and shall be payable on the Maturity Date.
     
          The Borrower shall pay interest on demand on any overdue
     principal hereof or overdue interest hereon from and including the
     date payment of such principal or such interest, as the case may
     be, was due to but not including the day of actual payment,
     calculated on a daily basis at a rate per annum which shall be
     equal to the sum of (i) 2% per annum and (ii) the interest rate
     applicable to this Note immediately before such amount became due.
     
          If an Event of Default (as defined in the Credit
     Agreement dated as of April 28, 1995 among the Borrower,
     the banks party thereto and Credit Suisse (New York
     Branch), as Administrative Agent (as the same may be
     amended from time to time)) shall occur and be continuing,
     then, in any such event, the Lender may by notice to the
     Borrower declare this Note and all interest hereon to be
     forthwith due and payable, without presentment, demand,
     protest or further notice of any kind, all of which are
     expressly waived by the Borrower; provided that in the
     event of an actual or deemed entry of an order for relief
     with respect to the Borrower under the Federal Bankruptcy
     Code, then without any notice to the Borrower or any other
     act by the Lender, this Note and all interest hereon shall
     automatically become due and payable, without presentment,
     demand, protest or other notice of any kind, all of which
     are hereby expressly waived by the Borrower.
     
          The Borrower hereby authorizes the Lender, if and to
     the extent any payment owed to the Lender is not made when
     due, to charge from time to time against any or all of the
     Borrower's accounts with the Lender any amount so due. The
     Borrower expressly waives diligence, presentment, demand,
     protest, notice of dishonor or other notice of any kind.
     This Note may be prepaid in whole or in part at any time
     upon three Business Days' notice.
     
          If this Note is repaid on any day other than the
     Maturity Date, the Borrower shall reimburse the Lender
     within 15 days after demand for any resulting loss or
     expense incurred by it, including (without limitation) any
     loss incurred in obtaining, liquidating or employing
     deposits from third parties, but excluding loss of margin
     for the period after any such payment; provided that the
     Lender shall have delivered to the Borrower a certificate
     as to the amount of such loss or expense, which certificate
     shall be conclusive in the absence of manifest error.
     
          If any payment on this Note shall be due and payable
     on a day which is not a Business Day, the date for payment
     shall be extended to the next succeeding Business Day and
     any extended time for the payment of principal or interest
     shall be included in computing interest at the rate this
     Note bears in connection with such payment.
     
          The failure of the Lender to exercise any rights
     hereunder shall not constitute a waiver thereof in that or
     any other instance.
     
          Neither this Note nor any provision hereof may be
     amended, modified, waived, discharged or terminated orally,
     but only by a statement in writing signed by the Borrower
     with the prior written consent of the Lender.
     
          All payments made on account of principal and interest
     hereof, may be recorded by the Lender and endorsed on the
     grid attached hereto, which is part of this Note; provided
     that the failure of the Lender to make such recordation or
     endorsement, or any error therein, shall not affect the
     obligations of the Borrower with respect to this Note.
     
           As used herein, "Business Day" means any day on which
     dealings  in Dollar deposits are carried on in  the  London
     interbank market and on which commercial banks are open for
     domestic  and foreign exchange business in London  and  New
     York City.
     
          THIS NOTE SHALL BE CONSTRUED IN ACCORDANCE WITH AND
     GOVERNED BY THE LAWS OF THE STATE OF NEW YORK.
     
          The Borrower irrevocably submits to the non-exclusive
     jurisdiction of any federal or New York State court
     sitting in New York City, and any appellate court from
     such court, in any suit, action or proceeding arising out
     of or relating to this Note, and hereby irrevocably
     waives, to the fullest extent permitted by law, any
     immunity from jurisdiction of any court or from any legal
     process the Borrower has or may hereafter acquire with
     respect to itself or its property in respect of its
     obligations under this Note.
     
     
     
                          LABORATORY CORPORATION OF AMERICA
                             HOLDINGS
                          
                         By: /s/ WESLEY R. ELINGBURG
                             -----------------------                     
                                 WESLEY R. ELINGBURG
                         Title: Executive Vice President and
                         Chief Financial Officer

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                       PAYMENTS OF PRINCIPAL AND INTEREST
                                        

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                                          Unpaid
                         Amount of       Principal    Amount of    Notification
             Date     Principal Repaid   Balance    Interest Paid    Made By
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