The present investigation was designed to understand the sublethal effects of cypermethrin, an active pyrethroid, a widely used against an extensive range of pests in agriculture. In this study Rohu (Labeo rohita) was subjected to the treatment with two sublethal concentrations (0.30mg/l and 0.15mg/l) of cypermethrin for a total period 10, 20 and 30 days. The results obtained indicated significant stress on the experimental fish due to pesticide intoxication.The histopathological study of the gill revealed changes as necrosis,vaculor degeneration, fusion of gill, twisting and shortening of secondary gills lamellae , atrophy of primary and secondary lamellae.