Large quantities of ground water have been pumped for many years in Texas from formations of Cretaceous, Eocene, Miocene, Pliocene, and Pleistocene age. Declines in water levels have resulted and investigations have been made by the Geological Survey in cooperation with the Texas Board of Water Engineers to determine the capacities of the formations to yield water to wells. The most reliable index of the quantity of water that a formation will yield has heretofore been considered to be the empirical correlation of pumpage and water levels in wells. Studies of recharge, laboratory studies of permeability and specific yield of water-bearing materials, and measurements of specific capacities of wells have also proven valuable.With the development of new methods, pumping tests have recently come into use. A pumping test and the use of its results are essentially a process of obtaining for the formation under investigation the equation of a water-level drawdown curve for a short period of time and extending the curve over a longer period by means of the equation. Predictions may thus be made of drawdowns caused by given rates of pumping. In making the predictions computed drawdowns must be adjusted for boundaries and changes in character of the formation not taken into account by the equation determined with the pumping test. Pumping tests have been made at Houston, Lufkin, Camp Swift, South Camp Hood, North Camp Hood, and Sweeny. The methods of making the tests, the results, and the use of the results are briefly described in this paper.