The 48-h straight-hinge larvae of Argopecten irradians were exposed for 9 days to various concentrations of zinc in seawater. The growth rate of larvae in the 50 ppb Zn mediums was 77% that of the controls, and nearly zero in the 200 ppb Zn mediums. A progressive decrease in growth and increase in larval deformity and mortality was observed with increasing zinc concentrations from 50 to 200 ppb. 50 and 100 ppb Zn resulted in delayed development of eye spot and metamorphosis and reduced numbers of larvae at both stages. All larvae subjected to higher zinc concentrations died before attaining the eye-spot stage. The zinc concentrations which caused 50% reduction in growth (G C50)and 50% mortality (LC 50)were 109 and 120 ppb respectively. Growing in the medium with 100 ppb Zn, the larvae fed with Isochysis galbana cultured in a medium with 100 ppb Zn showed more suppressed growth and development than those fed with nonnal food. It is suggested that zinc contaminated food has strong influence on the bay sca The 48-h straight-hinge larvae of Argopecten irradians were exposed for 9 days to various concentrations of zinc in seawater. The growth rate of larvae in the 50 ppb Zn mediums was 77% that of the controls, and nearly zero in the 200 ppb Zn mediums. A progressive decrease in growth and increase in larval deformity and mortality was observed with increasing zinc concentrations from 50 to 200 ppb. 50 and 100 ppb Zn induced in delayed development of eye spot and metamorphosis and reduced numbers of larvae at both stages. All larvae subjected to higher zinc concentration died before attained the eye-spot stage. The zinc concentrations which caused 50% reduction in growth (G C50) and 50% mortality (LC 50) were 109 and 120 ppb respectively. Growing in the medium with 100 ppb Zn, the larvae fed with Isochysis galbana cultured in a medium with 100 ppb Zn showed more suppressed growth and development than those fed with nonnal food. It is suggested that zinc contaminated food has strong influe nce on the bay sca