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                                                                   EXHIBIT 10.13

                               AMENDMENT NO. 2 TO
                              INCENTIVE STOCK PLAN



         The Martin Marietta Materials, Inc. Incentive Stock Plan, as amended
from time to time, (the "Plan") is hereby amended by this Amendment No. 2 as
follows, effective as of May 19, 1999.

         Section 2.09 of the Plan is amended and restated as follows:

                           "2.09 Identified Employee means an Eligible Employee
               (a) who is the Chief Executive Officer of the Corporation or an
               elected vice president of the Corporation, in each case unless
               the Committee, in its sole discretion, determines not to
               designate such officer as an Identified Employee, or (b) who is
               otherwise designated by the Committee as an Identified Employee
               for any Plan Year."

         All other terms and provisions of the Plan remain in full force and
effect.