Activity of tail, gut and muscle acid phosphatase ofRana tigrina tadpoles in relation to metamorphic index and temperature was studied. Optimum pH of the enzyme was between 4·0 and 4·5.Km for the muscle phosphatase was low, indicating its greater affinity to the substrate. With advancing stage of metamorphosis or increasing temperature, activity of the enzyme increased. At metamorphic climax the activity was low. Tail acid phosphatase displayed higher activity than the gut or muscle phosphatase, indicating the role of the enzyme in autolysis of the tail during metamorphosis.