Histopathological changes have been widely used as biomarkers in the evaluation of the health of fish exposed to contaminants, both in the laboratory and field studies. One of the great advantages of using histopathological biomarkers in environmental monitoring is that this category of biomarkers allows examining specific target organ including liver that are responsible for vital functions. Alternations found in these organs are normally easier identifying than functional ones. Quinalphos is one of the organophosphate insecticides represent one of the most widely used classes of pesticide with high potential for human exposure in both rural and residential environments The fresh water fish, Anabas testudineus was selected as the test animals. 1/10th of 96 hrs LC50 was taken as sublethal concentration of Quinalphos pesticide. After the stipulated period of exposure (24, 48, 72 and 96 hrs) fishes were sacrificed and liver was isolated and used for histopathological studies
