EXHIBIT 24.2

                                POWER OF ATTORNEY

         The undersigned  directors and/or officers of Ultramar Diamond Shamrock
Corporation, hereby constitute and appoint Timothy J. Fretthold and Todd Walker,
or either of them,  as the true and lawful  attorneys-in-fact  and agents of the
undersigned, each with full power of substitution and resubstitution,  to do any
and all acts and things in their names and in their  respective  capacities as a
director  and/or an officer of Ultramar  Diamond  Shamrock  Corporation,  and to
execute any and all  instruments  for them and in their names in the  capacities
indicated above, which said attorneys-in-fact and agents, or either of them, may
deem necessary or advisable to enable Ultramar Diamond  Shamrock  Corporation to
comply with the Securities Act of 1933, as amended,  and any rules,  regulations
and requirements of the Securities and Exchange  Commission in connection with a
Registration  Statement  on Form S-8,  including  without  limitation  power and
authority to sign for them,  in their name in the  capacities  indicated  above,
such Registration Statement and any and all amendments (including post-effective
amendments)  thereto, and to file the same, with all exhibits thereto, and other
documents in connection therewith,  with the Securities and Exchange Commission,
hereby ratifying and confirming all that the said  attorneys-in-fact and agents,
or their substitute or substitutes,  or any one of them, shall do or cause to be
done by virtue hereof.

/s/ Jean Gaulin                         /s/ Russell H. Herman
    Jean Gaulin                             Russell 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/ 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                         /s/ Robert S. Shapard
    W. H. Clark                             Robert S. Shapard

Dated: October 3, 2000