Three generations of brook trout (Salvelinus fontinalis) were exposed to several concentrations of total cadmium. Significant numbers of first- and second-generation adult males died during spawning at 3.4 micrograms Cd/liter. This concentration also significantly retarded growth of juvenile second- and third-generation offspring. The maximum acceptable toxicant concentration (MATC) for brook trout exposed to cadmium in Lake Superior water (hardness 44 mg/liter as CaCO3, pH 7-8) lies between 1.7 and 3.4 micrograms Cd/liter. Cadmium-residue analyses of kidney, liver, gill, gonad, spleen, muscle, and red blood cells from first- and second-generation trout indicated that kidney, liver, and gill tissue accumulated the greatest amounts of cadmium at each water exposure concentration. No significant increases in cadmium were measured in edible muscle at any of the cadmium water concentrations tested. Cadmium residues in kidney, liver, and gill tissue of fish from all exposure concentrations reached equilibrium (micrograms Cd/g tissue) in both first- and second-generation trout after 20 weeks.