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                                                                       Exhibit 5



             USX Corporation                  JOHN A. HAMMERSCHMIDT
             Law Department                   Assistant General Counsel-
             600 Grant Street                 Corporate & Assistant Secretary
             Pittsburgh, PA 15219-4776
             412 433 2922
             Fax: 412 433 2015



[USX LOGO]   October 13, 1999



             Securities and Exchange Commission
             450 Fifth Street, N.W.
             Washington, D.C. 20549

             Ladies and Gentlemen:

             I am Assistant General Counsel-Corporate and Assistant Secretary of
             USX Corporation, a Delaware corporation (hereinafter the
             "Corporation"), and have served as counsel to the Corporation in
             connection with the preparation of the Registration Statement on
             Form S-3 (hereinafter the "Registration Statement") for the
             proposed issuance of 3,385,000 shares of USX-Marathon Group Common
             Stock ("Marathon Stock") and 1,661,000 shares of USX-U.S. Steel
             Group Common Stock ("Steel Stock") (together, the "Shares") in
             connection with the Dividend Reinvestment and Direct Stock Purchase
             Plan for each class of stock.

             As Assistant General Counsel-Corporate and Assistant Secretary, I
             am familiar with the Corporation's Restated Certificate of
             Incorporation and its By-laws. I have also examined, or caused
             those acting under my supervision to have examined, the
             Registration Statement and such other records and documents that I
             have deemed necessary or desirable in rendering the opinion set
             forth below. In rendering such opinion, I have presumed the
             genuineness of all documents examined and the accuracy of all
             statements of fact contained therein.

             Based upon the foregoing, I am of the opinion that when the Shares
             have been duly authorized and executed by the Corporation and
             delivered against receipt of payment, the Shares will be legally
             issued, fully paid and non-assessable.

             I hereby consent to the filing of this opinion as an exhibit to the
             Registration Statement.

             Very truly yours,


             /s/ John A. Hammerschmidt