During 1963, 517 exploratory tests and 1,143 development wells were drilled in west-central Texas. Total activity was approximately the same as in 1962, but exploratory drilling increased 20.2 percent although successes decreased from 30.3 percent in 1962 to 22.5 percent in 1963. Development drilling decreased from 1,234 wells in 1962 to 1,143 wells in 1963. The areal distribution of successful exploratory tests in 1963 was similar to that of the past several years. A majority of the new discoveries were completed as oil producers, the most interesting being in the Mississippian of Nolan County. Seismic activity in west-central Texas decreased in 1963, but 36 gravity crew-weeks were reported.