Bottom sediments are a major reservoir for residues of the pesticide DDT and polychlorinated biphenyls (PCBs) released into aquatic environments. Fish consumption warnings or fishery closures in areas polluted by these chlorinated hydrocarbons are increasing. Thus, it is important to understand the processes by which such hydrophobic neutral synthetic organic compounds are incorporated into tissues of benthic seafood organisms. The fugacity model of bioaccumulation states that uptake is determined by the chemical fugacity differential between the organism and its environment. For benthic species the model most conveniently is tested by measuring residue concentrations in tissue and in the sediment to which the organism has been exposed. The authors describe such a test conducted through a field study of surficial sediments and a flatfish usedsuccessfully as a bioindicator for chlorinated hydrocarbon contamination in the Southern California Bight.