Heavy metal concentrations have been determined in fishes and shellfishes sampled from October 1971 to April 1972 in Korea. In general, fish viscera, shellfish muscle and crustacean exoskeleton contained high concentrations of the metals. With regard to the regional variations of the metals, samples of the west coast of Korea contained relatively high concentrations of mercury, copper, cadmium and lead, but those of the south coast contained high levels of cadmium and lead. In particular, the concentrations of copper in the samples of the west coast were almost twice as much those of the other coasts. The concentrations of mercury in the samples, as a whole, ranged from 0.02 to 0.58 ppm with an average of 0.16 ppm. The concentrations of cadmium were higher in the fish viscera and shellfish than the fish muscle, ranging from less than 0.02 to 0.78 ppm with an average of 0.12 ppm in the fish and shellfish muscle samples. The lead concentrations were slightly high in the fish viscera. In the muscle and bone of fish and shellfish, the range was 0.06-4.84 ppm with an average of about 1 ppm. The concentrations of copper were very high in the viscera of fish and shellfish. The shellfish muscle contained almost four times as much copper as in the fish muscle, particularly cephalopods, i. e., squid and octopus, contained very high levels of copper, and oysters collected from Gunsan area on the west coast contained the highest levels of copper. The concentrations of copper ranged from 0.12 to 28.7 ppm with an average of 1.4 ppm in the fish muscle and of 5.9 ppm in the shellfish muscle.