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                                  EXHIBIT (10A)


                                FOURTH AMENDMENT
                                       OF
                  USG CORPORATION SUPPLEMENTAL RETIREMENT PLAN

             (As Amended and Restated Effective as of July 1, 1997)


          WHEREAS, USG Corporation Supplemental Retirement Plan (the "Plan"),
established effective January 1, 1976 and amended from time to time, was last
amended and restated in its entirety effective as of July 1, 1997; and

          WHEREAS, further amendment of the Plan now is considered desirable;

          NOW, THEREFORE, pursuant to the authority delegated to the undersigned
by resolution of the Board of Directors of USG Corporation, the Plan be and is
further amended, effective November 8, 2000, by substituting the following for
subsection 5.3 of the Plan:

"5.3 FUNDING

          Benefits payable under this Plan to a Participant or a Supplemental
Plan Beneficiary shall be paid directly by the Employers from their general
assets in such proportion as the Company shall determine to the extent such
benefits are not paid from a Special Retirement Account (established pursuant to
Supplement A of this Plan) or pursuant to a Funding Agreement (as defined in
subsection 3.8) or from a so-called `rabbi trust,' an irrevocable grantor trust
the assets of which are subject to the claims of creditors of the Employers in
the event of their insolvency. The Employers shall not be required to segregate
on their books or otherwise any amount to be used for the payment of benefits
under this Plan, except as to any amounts paid or payable to a Funding Agreement
or to a `rabbi trust.'"

          IN WITNESS WHEREOF, the Company has caused these presents to be signed
on its behalf by an officer thereunto duly authorized this 11th day of April,
2001.

                                           USG CORPORATION

                                           By: /s/ Peter K. Maitland
                                              ---------------------------------
                                              Its: Vice President, Compensation,
                                              Benefits And Administration




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