AMENDMENT TO
                               UNILAB CORPORATION
                             2001 STOCK OPTION PLAN


         1. Effective February 6, 2002, Section 3(c) of Unilab Corporation 2001
Stock Option Plan ("2001 Plan") is hereby amended and restated in its entirety
to read as follows:

           (c)    Equitable Adjustment.

                    (i) Stock Dividends; Stock Splits; Reverse Stock Splits. In
           case the Company shall (1) pay a dividend or make any other
           distribution with respect to its Common Stock in shares of its
           capital stock, (2) subdivide its outstanding Common Stock, or (3)
           combine its outstanding Common Stock into a smaller number of shares,
           the number of shares of Common Stock issuable upon exercise of the
           Options immediately prior to the record date for such dividend or
           distribution or the effective date of such subdivision or combination
           shall be adjusted so that the holder of the Options shall thereafter
           be entitled to receive the kind and number of shares of Common Stock
           or other securities of the Company that such holder would have owned
           or have been entitled to receive after the happening of any of the
           events described above, had such Options been exercised immediately
           prior to the happening of such event or any record date with respect
           thereto. An adjustment made pursuant to this Section 3(c) shall
           become effective immediately after the effective date of such event
           retroactive to the record date, if any, for such event.

                    (ii) No Adjustment for Dividends; No Adjustment of Option
           Price. Except as otherwise provided in this Section 3(c), no
           adjustment in respect of any ordinary (or except as the Board of
           Directors may expressly determine otherwise to be equitable,
           extraordinary) dividends declared and paid on Common Stock, or on any
           other capital stock of the Company, shall be made during the term of
           an Option or upon the exercise of an Option. Notwithstanding anything
           to the contrary contained in this Plan, in the event of any
           adjustments to Options pursuant to this Section 3(c), adjustments
           shall be made solely to the number and kind of securities purchasable
           upon the exercise of Options and no adjustments shall be made to the
           Option exercise price.

                    (iii) Other Adjustments. In the event that at any time, as a
           result of an adjustment made pursuant to this Section 3(c), the
           registered holders of Options shall become entitled to receive any
           securities of the Company other than shares of Common Stock,
           thereafter the number of such other securities so receivable upon
           exercise of the Options shall be subject to adjustment from time to
           time in a manner and on terms as nearly equivalent as practicable to
           the provisions with respect to the shares of Common Stock contained
           in this Section 3(c).

                    (iv) Purchase Rights Upon Merger, Consolidation, etc. In the
           event of any consolidation of the Company with or merger of the
           Company with or into another corporation or in case of any sale,
           transfer or lease to another entity of all or substantially all the
           assets of the Company, the Company may, without the consent of the
           Option holder, cancel any outstanding Option (whether vested or
           unvested) held by the holder and make a cash payment to the holder in
           consideration for such cancellation of such amount the Committee, in
           its sole discretion, deems appropriate. Such payment shall be, in
           respect of any vested Option, absent any determination made by the
           Committee in its sole discretion to the contrary, equal to the
           positive difference between the aggregate Fair Market Value of the
           shares subject to such Option and the aggregate exercise price of
           such Option. To the extent that the Company does not cancel Options
           as described in this Section 3(c)(iv), the Acquiring Person (as
           defined below) shall execute an agreement under which the Acquiring
           Person shall assume each Option and each such assumed Option shall
           continue to vest and become exercisable in accordance with its terms
           (adjusted, in the discretion of the Board of Directors, to reflect
           the effect of such transaction) and shall thereafter become
           exercisable, subject to the conditions and other terms of such
           Options, for the number and/or kind of capital stock, securities
           and/or other property into which the Common Stock subject to the
           Option would have been changed or exchanged had the Option been
           exercised in full prior to such transaction, provided that, if
           necessary, the provisions of the Option shall be appropriately
           adjusted so as to be applicable, as nearly as may reasonably be, to
           any shares of capital stock, securities and/or other property
           thereafter issuable or deliverable upon exercise of the Option. In
           the event that this Section 3(c)(iv) shall be applicable, the
           provisions of Sections 3(c)(i) through (iii) shall not be applicable.
           For purposes of this Section 3(c), Acquiring Person shall mean, (1)
           the continuing or surviving entity of a consolidation or merger with
           the Company in connection with which the Common Stock is changed into
           or exchanged for stock or other securities of any other entity or
           cash or any other property, (2) the transferee of all or
           substantially all of the assets of the Company, (3) the parent entity
           of any corporation consolidating with or merging into the Company in
           a consolidation or merger in connection with which the Common Stock
           is changed into or exchanged for stock or other securities of any
           other entity or cash or any other property if the Company becomes a
           subsidiary of such entity and the parent entity of any entity
           acquiring all or substantially all of the assets of the Company, or
           (4) in the case of a capital reorganization or reclassification or in
           any case in which the Company is a surviving corporation in a merger
           not described in clause (1) or (3) above, the Company.

(v)           Notice of Adjustment. Whenever the number of shares of Common
              Stock purchasable upon the exercise of an Option is adjusted, as
              herein provided, the Company or the Acquiring Person shall give
              notice to each holder of such adjustment or adjustments.

         2.Except as amended herein, the 2001 Plan shall remain in full force
and effect.

* Approved by action of the Board of Directors on February 6, 2002.