Exhibit 24.2


                         POWER OF ATTORNEY
 

KNOW ALL PERSONS BY THESE PRESENTS, that the undersigned hereby constitute
and appoint Patrick J. Guarino, Curtis V. Anastasio, Harold D. Mallory, and
Todd Walker, and each of them, his or her true and lawful attorney or
attorneys-in-fact, with full power of substitution and revocation, for the
undersigned and in the undersigned's name, place, and stead, in the
undersigned's capacity as an officer and/or director of ULTRAMAR DIAMOND
SHAMROCK CORPORATION (the "Corporation"), to sign a Registration Statement
on Form S-3, as promulgated by the Securities and Exchange Commission (the
"Commission"), for the purposes of registering, pursuant to the Securities
Act of 1933, as amended, debt and equity of the Corporation and one or more
of its subsidiaries in amounts not to exceed $900,000,000 in the aggregate, 
and to sign any or all amendments and any or all post-effective amendments
to such Registration Statements, and to file the same, with all exhibits
thereto, and other documents in connection therewith, with the Commission
granting unto said attorney or attorneys-in-fact, and each of them, full
power and authority to do and perform each and every act and thing requisite
and necessary to be done in connection with such registration, as fully to
all intents and purposes as he or she could do in person, hereby ratifying
and confirming all that said attorney or attorneys-in-fact or any of them or
their substitute or substitutes may lawfully do or cause to be done by virtue
hereof.


/s/ R. R. Hemminghaus                       /s/ Jean Gaulin
    R. R. Hemminghaus                           Jean Gaulin


/s/ H. Pete Smith                           /s/ Russel H. Herman
    H. Pete Smith                               Russel H. Herman


/s/ Byron Allumbaugh                        /s/ Bob Marbut
    Byron Allumbaugh                            Bob Marbut


/s/ E. Glenn Biggs                          /s/ Katherine D. Ortega
    E. Glenn Biggs                              Katherine D. Ortega


/s/ W. E. Bradford                          /s/ Madeleine Saint-Jacques
    W. E. Bradford                              Madeleine Saint-Jacques


/s/ H. Frederick Christie                   /s/ C. Barry Schaefer
    H. Frederick Christie                       C. Barry Schaefer


/s/ W. H. Clark
    W. H. Clark

Dated:  June 4, 1997

W5119.tw