The present study investigated the growth inhibitory potential of partially purified protease inhibitors from Subabul (Leucaena leucocephala) on Common cutworm Spodoptera litura (Fabricius) which has attained major pest status in India. Second instar larvae given treated diet (25, 50 100, 200, 400 and 800 __ampersandsignmu;g/ml) showed a decrease in larval period with increase in concentration when compared with control whereas total developmental period increased at lower concentrations but decreased at 400 and 800__ampersandsignmu;g/ml in comparison to control. The percentage pupation and emergence of females was inhibited and longevity of adults was reduced with increase in concentration. Percentage of male emergence increased significantly at highest concentration in comparison to control. No egg laying was observed at 400 and 800__ampersandsignmu;g/ml concentrations. A significant decline in percent hatching upto 200__ampersandsignmu;g/ml was noticed. The relative growth rate, consumption rate and efficiency of conversion of ingested and digested food was significantly reduced. The present findings clearly confirmed the potential of the inhibitor for pest control.