EXHIBIT 21 SUBSIDIARIES OF THE REGISTRANT Clayton Williams Energy, Inc. has four wholly owned subsidiaries as follows: - Warrior Gas Co., a Texas corporation, which has a wholly owned subsidiary, Clajon Industrial Gas, Inc., a Texas corporation - Clayton Williams Trading Company, a Texas corporation - Clayton Williams Venezuela, Inc. (formerly Clayton Williams Argentina, Inc.), a Delaware corporation - CWEI Acquisitions, Inc. (formerly Texas Energy Company), a Delaware corporation - Clayton Williams Midland, Inc., a Texas corporation