EXHIBIT 21 Central And South West Corporation Subsidiaries of the Registrant As of December 31, 1997 Company Name Business Conducted State or Jurisdiction Under Same Name of Incorporation/Formation - ------------------------------------------------------------------------------- Central Power and Light Company Texas 539 North Carancahua Street Corpus Christi, Texas 78401-2802 CPL Capital I Delaware 1616 Woodall Rodgers Freeway Dallas, Texas 75202-1234 Public Service Company of Oklahoma Oklahoma 212 East 6th Street Tulsa, Oklahoma 74119-1212 PSO Capital I Delaware 1616 Woodall Rodgers Freeway Dallas, Texas 75202-1234 Southwestern Electric Power Company Delaware 428 Travis Street Shreveport, Louisiana 71156-0001 SWEPCO Capital I Delaware 1616 Woodall Rodgers Freeway Dallas, Texas 75202-1234 West Texas Utilities Company Texas 301 Cypress Street Abilene, Texas 79601-5820 SEEBOARD, plc United Kingdom Registered Office Forest Gate, Brighton Road Crawley, West Sussex RH11 9BH Central and South West Services, Inc. Texas 2 West Second Street Tulsa, Oklahoma 74103-3102 and 1616 Woodall Rodgers Freeway Dallas, Texas 75202-1234 C3 Communications, Inc. Delaware 1705 South Capital of Texas Highway - Suite 400 Austin, Texas 78746 CSW Credit, Inc. Delaware 1616 Woodall Rodgers Freeway Dallas, Texas 75202-1234 CSW Energy, Inc. Texas 1616 Woodall Rodgers Freeway Dallas, Texas 75202-1234 CSW Energy Services, Inc. Texas 1616 Woodall Rodgers Freeway Dallas, Texas 75202-1234 Company Name Business Conducted State or Jurisdiction Under Same Name of Incorporation/Formation - ------------------------------------------------------------------------------- CSW International, Inc. Delaware 1616 Woodall Rodgers Freeway Dallas, Texas 75202-1234 CSW Leasing, Inc. Delaware 1616 Woodall Rodgers Freeway Dallas, Texas 75202-1234 EnerShop Inc. Delaware 1616 Woodall Rodgers Freeway Dallas, Texas 75202-1234