Hatching times (50% hatch) and hatching rates of red sea bream, Pagrus major eggs incubated in 10^-5M single amino acid solutions with artificial seawater were investigated. The eggs were introduced into the culture media at the stage of heart-beat initiation. Hatching times in the media of L-glutamic acid, taurine, L-tryptophan, L-proline and L-cystine were significantly shorter than incontrol artificial seawater. The branched amino acids such as L-valine, L-isoleucine and L-leucine reversely delayed the hatching time as compared with the control. A linear correlation between hatching time (X) and hatching rate (Y) was noted; Y=242.6-147.2X (r=-0.75) . These results suggest that some amino acids can advance hatching time and increase hatching rate of red sea bream eggs, possibly through the promotion of hatching enzyme secretion or the differentiation and formation of organs.