Abstract: TNT, BHC, DDT, Parathion and HgCl2 were used separately in acute toxicity tests on the Silver Carp, Hypophthalmichthys molitrix. Serum glutamic oxalocetie transaminase activity level in the treated fish was significantly increased. Glutamic pyruvic transaminase level was effected by Parathion. The degree of elevation of serum trausaminase activity is related to the concentration of mercuric chloride.The age and species of various Chinese freshwater Cyprinids, different types of water bodies, short term starvation, disturbance and cage culture all had no effect on serum transaminase activity.But a rise in water temperature or an impoverishment of dissolved oxygen content to a level below 1 ppm increased fish serum glutamic oxalocetie transaminase and glutamic pyruvic transaminase activity. Pish serum glutamic oxalocetie transaminase activity is correlated to water temperature.