Diethylphthalate is a plasticizer widely used in the manufacture of plastics, cosmetics, cellulose ester films, medical devices and many commercial products. These esters have been detected in the waterways and suspected to exhibit estrogenic activity. Resultantly, diethylphthalate could have adverse impact on the aquatic biota. This research paper reports the changes induced by diethylphthalate on the tissue damaging enzyme activity like Acid phosphatase (ACP), Alkaline phosphatase (ALP), Sorbitol dehydrogenase( SDH) , Lactate dehydrogenase (LDH) of gill , liver and muscle of Tilapia Oreochromis mossambicus . The fishes were exposed to diethylphthalate for a period of seven days at two different concentrations ( 5ppm and 15ppm ) . Significant alternation in the ACP, ALP, SDH and LDH activity of gill,liver and muscle were evinced in diethylphthalate exposed fishes. ACP activity significantly decreased in the gill, whereas significantly elevated in the liver and muscle of Tilapia Oreochromis mossambicus when compared to the control. ALP activity of gill significantly elevated and that of liver and muscle significantly declined in diethylphthalate exposed fishes. SDH activity of gill, liver and muscle significantly declined whereas, LDH activity significantly enhanced in the gill, liver and muscle when compared to unexposed ones. Thus the altered enzyme activity evinced in this study suggests that diethylphthalate could cause metabolic changes in Oreochromis mossambicus
