1 EXHIBIT 23 [LETTERHEAD] March 23, 2000 Permian Basin Royalty Trust Bank of America, N.A., Trustee 901 Main Street Dallas, Texas Gentlemen: Cawley, Gillespie & Associates, Inc. hereby consents to the use of the oil and gas reserve information in the Permian Basin Royalty Trust Securities and Exchange Commission Form 10-K for the year ending December 31, 1999 and in the Permian Basin Royalty Trust Annual Report for the year ending December 31, 1999, based on reserve reports dated March 21, 2000 prepared by Cawley, Gillespie & Associates, Inc. Submitted, /s/ CAWLEY, GILLESPIE & ASSOCIATES -------------------------------------- CAWLEY, GILLESPIE & ASSOCIATES, INC.