Accumulation, transfer, and loss of Kepone in estuarine organisms were studied in laboratory bioassays. Kepone was bioconcentrated by oysters (Crassostrea virginica), mysids (Mysidopsis bahia), grass shrimp (Palaemonetes pugio), sheepshead minnows (Cyprinodon variegatus), and spot (Leiostomus xanthurus), from concentrations as low as 0.023 micrograms/l seawater. Bioconcentration factors ranged from 10 to 340 in static exposures and 900 to 13,500 in flow-through bioassays, and were dependent on species and exposure duration. Depuration of Kepone from oysters in Kepone-free water was rapid (35% loss in 24 hours); however, depuration of Kepone was slow in crustaceans and fish, with tissue concentrations decreasing 30-50% in 24-28 days. Oysters, fed Chlorococcum containing approximately 34 micrograms Kepone/g wet weight, attained 0.21 micrograms Kepone/g (wet tissue) in 14 days, but when fed Kepone-free plankton, depurated Kepone to below detectable concentrations (<.02 micrograms/g) within 10 days. Spot obtained Kepone when fed live mysids that had grazed on Kepone-laden brine shrimp. Kepone residues (1.05 micrograms/g wet tissue) in these fish approached the concentration of their food (1.23 micrograms/g wet tissue); at the lower concentration tested, Kepone concentrations below detection limits (<.2 micrograms/g) in prey accumulated in the predator to detectable concentrations (0.02 micrograms/g) within 30 days.