The Antlers aquifer, which consists of as much as 900 feet of friable sandstone, silt, clay, and shale, crops out in an area of 1,860 square miles and underlies about 4,400 square miles in southeastern Oklahoma. Precipitation ranges from 35 to 50 inches per year across the outcrop area, which is well suited to allow high rates of infiltration. The aquifer contains an estimated 31,600,000 acre-feet of water having less than 1,000 milligrams per liter dissolved solids. The average saturated sand thickness is 250 feet. Aquifer tests in the confined part of the aquifer give an average storage coefficient of 0.0005 and an average transmissivity of 1,480 feet squared per day. The estimated specific yield of the unconfined part of the aquifer is 0.15; the transmissivity has not been determined. Large-capacity wells tapping the aquifer commonly yield 100 to 500 gallons per minute; the maximum measured yield is 1,700 gallons per minute. Water usage from the aquifer is very small owing to the availability of an abundance of surface water. Water quality throughout the central and northern part of the aquifer is generally acceptable for municipal use. A few wells, however, yield water containing concentrations of iron and manganese exceeding the limit recommended for municipal use by the National Academy of Sciences and National Academy of Engineering (1972).