Gills are the prime organs for gaseous exchange and perform several other physiological functions including osmoregulation and excretion. Harmful effects of several pesticides on the gill histomorphology are well known. In this paper the effects of heavy metal on the gills of Clarias batrachus is demonstrated. Clarias batrachus, a freshwater teleost were exposed to copper sulphate for 24, 48, 72 and 96 h at 0.25, 0.30, 0.35 and 0.40 ppm to determine the LC50 values as well as any histopathological changes to the gills .The histological sections of gills of snake headed air breathing teleost examined under light microscope showed severe structural alterations like mucus cells hyperplasia, bulging of taste buds, formation of interlamellar bridge and sub epithelial spaces in the primary and secondary gill lamellae.