The effect, of seven factors was studied on the activity of hepatopancreatic sucrase ofMacrobrachium lamarrei. Its optimum pH is 6·0 and optimum temperature 50° C and its activity was suppressed by the two end products, glucose and fructose. On prolonging incubation period sucrase activity remained constant up to 8 hr, declined thereafter, finally becoming zero. Increasing enzyme concentration produced a similar effect. Its Km value is 4·5 × 10−2 M. Dialysis suppressed its activiiy by 17·9%.