In recent years, exploration and mining of uranium have become a significant part of the Texas mineral scene, with Texas emerging as a leading uranium-producing state. At the end of 1970, Texas ranked third in reserves among the states, with ore reserves of 6.6 million tons. Continuation of the recent high level of exploration is shown by the 6.1 million feet of drilling in Texas during 1970, surpassed only by drilling activity in Wyoming. This guidebook is a reprinting of a field trip guidebook originally printed by the Houston Geological Society for the annual meeting of the American Association of Petroleum Geologists held in Houston, April 1971. This field guide should serve as a valuable reference to the important uranium mineral district in South Texas.