Exhibit 10.19

                    Amendment No. 1 to Stock Option Agreement


      This Amendment No. 1, dated as of January 20, 1997, to the Stock Option
Agreement dated as of October 20, 1992 (the "Stock Option Agreement"), is
entered into by and between Unilab Corporation, a Delaware corporation (the
"Corporation") and Andrew H. Baker (the "Option Holder").

      The Stock Option Agreement is hereby amended as follows:

      1. Section 1 is amended by deleting the final sentence thereof, with the
         effect of immediately vesting all options.

      2. Section 3 is amended by (i) adding to the first sentence thereof, after
         the word "to" and before the word "a", the words "all or"; and (ii)
         deleting the second sentence thereof in its entirety and replacing it
         with the following sentence: "The Option Holder's right to exercise the
         aforementioned Option shall expire on January 20, 2007 (the "Expiration
         Date").

      3. Section 4(ii) is amended by adding the word "siblings" after the word
         "parents" and before the word "spouses".

      4. Section 5 is deleted in its entirety and the section numbers thereafter
         are renumbered appropriately.

      5. Sections 6(a) and 6(b) are deleted in their entirety and replaced by
         the following: "Option Holder shall be entitled to exercise the Option
         through the Expiration Date notwithstanding termination of Option
         Holder's employment by the Corporation prior to the Expiration Date".

      6. Section 9 is hereby deleted in its entirety and replaced with the
         following:

         8. Mergers, Recapitalizations and Dissolutions. The "acquisition" of
            the Corporation by another entity shall cause each outstanding
            option to become an option to purchase shares of the acquiring
            entity, for the balance of the term of the option, at a price and
            for a number of shares as is consistent with the acquisition terms,
            notwithstanding any contrary provision in the Stock Option Program
            in accordance with which this option was granted. The "acquisition"
            of the Corporation by another entity shall be defined to be either a
            merger or consolidation with an acquiring entity (or subsidiary or
            affiliate thereof) in which the Corporation is not the surviving
            entity or in which the Corporation becomes a subsidiary of an
            acquiring entity;


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         the sale of substantially all of the Corporation's assets; or the
         dissolution or liquidation of the Corporation.

      Except as expressly provided above, the Stock Option Agreement shall
remain in full force and effect.

      This Amendment No. 1 shall be governed by and construed in accordance with
the laws of the State of Delaware, other than its conflicts of laws provisions.


      OPTION HOLDER                                  UNILAB CORPORATION
                                                
                                                
                                                
      __________________________                 By: ___________________________
Name: Andrew H. Baker                            Name:
                                                 Title: