Flow-through, 96-hr bioassays were conducted to determine the acute toxicity of technical BHC and lindane to several estuarine animals. Test animals and their respective 96-hr lindane LC50 values were: mysid (Mysidopsis bahia), 6.3 micrograms/L; pink shrimp (Penaeus duorarum), 0.17 micrograms/L; grass shrimp (Palaemonetes pugio), 4.4 micrograms/L; sheepshead minnow (Cyprinodon variegatus), 104 micrograms/L; and pinfish (Lagodon rhomboides), 30.6 micrograms/L. The 96-hr LC50 values for pink shrimp and pinfish exposed to BHC were 0.34 and 86.4 micrograms/L, respectively. Two BHC bioconcentration studies were conducted with the oyster, Crassostrea virginica, and pinfish. After 28 days exposure, oysters bioconcentrated an average of 218 X the BHC measured in exposure water, while pinfish bioconcentrated 130 X in their edible tissues and 617 X in offal. After one week in BHC-free sea water, no detectable residues were measured in oysters or pinfish. (Copyright (c) Springer-Verlag New York Inc. 1977.)