The cute toxicity test of mercury, cadmium and copper to yellowtail, Seriola quinqueradia, and to rock-bream, Oplegnathus fasciatus, were conducted by static bioassays from 18 July to 27 October, 1978. In the tests, tile least sensitive heavy metals were cadmium to rock bream and copper to yellowtail. The test species were most sensitive to mercury among all the chemicals used. The 24hr-LC 50 value for the yellowtail was 0.11mg/l for mercury, 0.82mg/l for cadmium and 1.03mg/l for copper. While the 48hr-LC 50 value for the rock bream was 1.40mg/l for mercury and 1.73mg/l for copper.