Bruchid larvae cause major losses in grain legume crops throughout the world. Some bruchid species, such as the cowpea weevil and the Mexican bean weevil, are pests that damage stored seeds. Vicilin 7S storage proteins isolated from different legume seeds have been implicated as antibiosis factors against insects, particularly the cowpea weevil, Callosobruchus maculatus. In this study, Vicilins from Crotalaria pallida (CpV) seeds were purified by ammonium sulphate precipitation followed by chitin affinity and gel filtration Sephacryl S300 chromatographies. Vicilin isolated was evaluated by SDS-PAGE and showed tree protein bands Mr around 46-66 kDa. CpV was assayed for anti-insect activity at different concentrations (0.06 - 1% w/w) against C. maculatus (cowpea weevil) and Z. subfasciatus (Mexican bean weevil) larvae. Infestation on artificial seeds was accomplished by placing tree 2 days old females in a vial containing four seeds for 24 hours at 28^o C, 50% RH. The excess eggs laid were removed leaving three eggs in each seed. Each treatment was run in triplicate. After 20 days, artificial seeds were opened and larvae were counted and weighted to determine WD₅₀ and LD₅₀. Controls were made without presence of vicilins. CpV had a WD₅₀ of 0.21 and a LD₅₀ of 0.28 for C maculatus larvae and a WD₅₀ of 0.14% and a LD₅₀ of 0.85% for Z. subfasciatus. Regression analysis showed that for each increase of 0.1% of vicilins content was observed a mass decrease of 0.005% for C. maculatus larvae and 0.004% mass decrease for Z. subfasciatus larvae. Both larvae were dissected to remove the whole midguts which were submitted to Von Wisselingh test to chitin detection. Presence of chitin was confirmed in both samples. The strong effects of CpV should be explained by binding of vicilins to chitin present in midgut from both bruchids.