Ametryne is a commonly used synthetic herbicide. It is used for eradication of water hyacinth. The present study was carried out to investigate the toxic effects of ametryne on common carp, Cyprius carpio. Sub chronic toxicity study was carried out by inoculation of 1 and 2 ppm dose for 4 weeks. Hematological and biochemical parameters were investigated during exposure to different sub lethal concentrations of ametryne under controlled conditions. The following observed changes were statistically significant: decrease in total erythrocyte count, packed cell volume, hemoglobin concentration, total leuckocytic count and total protein, and increases in glucose, GOT and GPT.