In the present study, the effects of 0.20 and 0.35 ppm azinphosmethyl exposures occurring on days 1, 2, 3, 4, and 15 for on serum enzyme activities and protein and glucose levels in blood, muscle, and liver tissues of fish, Cyprinus carpio (L.), were photometrically investigated. Protein and glycogen contents in muscle and liver tissues were also determined. Azinphosmethyl did not affect the level of total protein in serum. However, there was a decrease in the level of muscle protein in 3 days of treatement while the liver protein elevated after acute exposure to both concentration of azinphosmethyl. it was also found that there was an elevation in the serum glucose content while the muscle and liver glycogen contents were reduced. Serum enzyme activities were also altered. Glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase activities initially increased following exposure to both concentrations of azinphosmethyl; later there was no change in the activities of these enzymes. Lactate dehydrogenase enzyme activity also increased in thr beginning of the experiment, but it was at the control level in 15 days. Alkaline phosphatase enzyme activity decreased on the first of day treatment while it increased second day. However, there was no significant difference during the other exposure times. After acute exposure to 0.35 ppm concentration of azinphosmethyl there was a significant increase in acid phosphatase activity while there was no change in this enzyme activity at the other exposure concentration and periods. Furthermore, sublethal concentrations of azinphosmethyl caused the behavioral and morphological changes in C. carpio. The results of this study showed that tissue necrosis and an elevation of glycogenolysis occurred following acute exposure to azinphosmethyl, but compensatory mechanisms were developed by C. carpio during chronic expo sure. (C) 1998 Academic Press.