Exposure of three generations of brook trout (Salvelinus fontinalis) to mean total lead concentrations (0.9-474 microg/l) showed that all second-generation trout exposed to 235 and 474 microg Pb/l and 34% of those exposed to 119 microg Pb/l developed severe spinal deformities (scoliosis). Scoliosis also appeared in 21% of the newly hatched third-generation alevins exposed to 119 microg Pb/l, and weights of these fish 12 wk after hatch were significantly reduced. Gill, liver, and kidney tissues of first- and second-generation brook trout accumulated the greatest amount of lead. Only small amounts accumulated in the edible muscle. An equilibrium of lead residues was reached in liver and kidney tissue from second-generation fish after 70 wk of exposure, but not in gill tissue. The maximum acceptable toxicant concentration (MATC) for brook trout in water with a hardness of 44 mg/liter (as CaCO3) and a pH of 6.8-7.6 lies between 59 and 119 microg/liter for total lead and between 39 and 84 microg/liter for dissolved lead.