A DDT manufacturin/!; plant that operated on the Redstone Arsenal near Huntsville, Alabama dischar/!;ed DDT-laden effluent from 1947 to 1970 into a creek on Wheeler National Wildlife Refu/!;e. Seven to 9 years after the plant closed, high DDT, DDE, and DDD levels were reported in soils, river sediments, and fish in the area. Eleven of 27 mallards (Anas platyrhynchos) collected on the Refu/!;e during February 1979 had carcass DDE residues that exceeded levels associated with e/!;gshell thinning. DDE residues in a smaller number of mallards exceeded levels associated with egg breakage, poor hatchability, and abnormal behavior and poor survival of offspring. Several avian species have disappeared from the Refuge since 1950, prohahly due to hoth industrial discharges of DDT from the plant and insecticidal use of DDT in the area. The contamination still presents a threat to herons, waterfowl, and raptors including occasional wintering or migrant eagles (Haliaeetus leucocephalus), and prohahly many other avian species. A maternity colony of endangered gray hats (Myotis grisescens) is also threatened by this contamination.