The fingerlings of Catla catla were exposed to sublethal concentrations of profenophos (10% and 30% SLC of 96 hrs LC₅₀) for a period of 10, 20 and 30 days. The alteration in biochemical composition (carbohydrate, protein and lipid) of gill, intestine, kidney, liver and muscle tissues were investigated. In the biochemical study, values of carbohydrate, protein and lipid content showed a gradual decrease with increase in dose of profenophos and exposure periods.