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Between 1988 and 1990 the Daphne, Alabama Field Office, U.S. Fish and Wildlife Service FWS conducted a contaminant study on the Tombigbee River near McIntosh, Alabama. Fish and sediment samples were collected and analyzed for mercury and DDT, two contaminants determined from earlier investigations as occurring in the rivers biota at concentrations of concern. The results of our study are presented in the enclosed report entitled An Evaluation of Mercury and DDT Contamination in Fish and Sediments Collected from the Tombigbee River Near McIntosh, Alabama. Total DDT concentrations in whole body samples of largemouth bass ranged from 0.36 ppm to 34.52 ppm.parts per million. Levels in the edible portions, filets, were considerably less ranging from 0.08 ppm to 2.22 ppm. Approximately 50 of the fish collected during the 1990 survey were found with DDE residues exceeding 3.0 ppm, a concentration documented as causing egg shell thinning in consuming avian species. As a result, fish eating species, i.e., bald eagles, herons, egrets, etc., forging in this area of the river could be subject to a decrease in reproductive success. Detectable levels of mercury were found in all fish samples analyzed. Contrary to the DDT findings, the higher mercury values occurred in the edible portions rather than the whole body. Concentrations in filet samples ranged from 0.08 ppm to 0.67 ppm with a mean of 0.37 ppm while whole body samples ranged from 0.07 ppm to 0.50 ppm with a mean of 0.23 ppm. In addition, whole body mercury concentrations of 1.89 ppm have been reported in fish collected from a lake within the study area that is flooded during annual high river stages. FWS research investigations have documented that reproduction in waterfowl has been significantly impaired when the birds were fed a diet containing 0.50 ppm mercury. The aforementioned lake provides an apparently attractive wintering habitat for a number of ducks and wading birds that eat fish and invertebrates. There is a concern that the mercury concentrations in the lakes biota could be adversely affecting the reproduction of these birds. Since 1964 the Fish and Wildlife Service has maintained a national monitoring network collecting fish samples throughout the country. These samples are analyzed for a number of contaminants including DDT and mercury. One of the network stations is located on the Alabama River at Chrysler, Alabama, which is a drainage adjacent to the Tombigbee River. In contrast to the elevated levels of contaminants in the Tombigbee River, during the period of record for the network, DDT concentrations in fish taken at Chrysler have not exceeded 0.32 ppm and mercury has not been found above 0.22 ppm. The FWS is anticipating conducting additional studies to track the migration of these contaminants through the higher trophic levels of the food web, principally avian species foraging along the river system.