The experiment was designed to determine the effect of suspended clay sediments on the bioconcentration of the chlorinated hydrocarbon pesticide Kelthane (dicofol, 4-chloro-a-(4-chlorophenyl)-a-(trichloromethyl) benzene methanol) in fathead minnows (Pimephales promelas). The test was carried out under continuous-flow conditions with a modified Mount-Brungs toxicant dilution apparatus and an exposure period of 28 days. Two known safe Keltane treatment levels were tested in both filtered lake water and lake water containing approximately 65 mg/L of clay particles. The clay sediments decreased bioconcentration in fathead minnows by 35%, indicating that the 30+% of total Kelthane sorbed onto clay was biologically unavailable to the fish. Bioconcentration factors at the two Kelthane concentrations were not significantly different. Steady-state concentrations were estimated to occur in 39 to 60 days of exposure at 9,500 to 18,900 times water level.