Recent contamination of the James River estuary, Virginia, with Kepone prompted acute flow-through bioassays to determine the 96-hour toxicity of the insectivide to four estuarine species native to that ecosystem. The species and their 96-hour LC50 values were: grass shrimp (Palaemonetes pugio), 121 μg/liter; blue crab (Callinectes sapidus), >210 μg/liter; sheepshead minnow (Cyprinodon variegatus), 69.5μg/liter; and spot (Leiostomus xanthurus) 6.6μg/liter. Surviving animals were analyzed for Kepone. Average bioconcentration factors (the concentration of Kepone in tissues divided by the concentration of Kepone measured in seawater) were: grass shrimp, 698; blue crab 8.1; sheepshead minnow, 1,548; and spot, 1,221.