Samples of various tissues and organs from healthy California sea lions (Zalophus californianus californianus) and sick animals (apparently with leptospirosis) collected along the central Oregon coast in 1970, 1971, and 1973 were analyzed for total mercury, methylmercury, cadmium, and chlorinated hydrocarbons. Maximum mercury concentrations of 74–170 ppm occurred in sea lion liver, but only 1.6–3.7% of this was present as methylmercury. Cadmium was concentrated primarily in the kidney which contained 7.2–12.0 ppm of the metal. Chlorinated hydrocarbon residues in sea lion fat ranged between 253–475 ppm DDE, and 21.2 and 34.1 ppm PCB. Although mercury, cadmium, and chlorinated hydrocarbon residues in some of the sick sea lions were significantly higher than those present in healthy animals, it is not possible to relate these differences to the onset of leptospirosis.