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                                                                       EXHIBIT 5
March 8, 1995
 
Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C. 20549
 
Ladies and Gentlemen:
 
I am Assistant General Counsel 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 sale of 3,200,000
shares of USX-Marathon Group Common Stock (the "Shares") pursuant to the
USX-Marathon Group Common Stock Dividend Reinvestment and Stock Purchase Plan.
 
As Assistant General Counsel, I am familiar with the Corporation's 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, including certificates of government officials and
corporate officers, 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 the Shares, when issued, 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