This study was conducted to identify the individual biochemical factors involved in the resistance observed in a few Mexican bean accessions against the bean weevil, Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae). Soluble proteins from different bean genotypes were separated by fractionated acetone precipitation. Insects were reared on artifical seeds composed of a susceptible background bean flour enriched with the different protein fractions. At low doses (2% w/w), the 0–20% and 20–40% acetone fractions of the resistant bean accessions G 12954 and G 12880 inhibited larval growth of the bean weevil, but not of a related species, the Mexican bean weevil, Zabrotes subfasciatus (Boheman). The 0–20% fraction caused the highest mortality of first instar larvae. The 60–80% acetone fraction contains general resistance factors, like α-amylase and protease inhibitors, which when enriched in artifical seeds led to a strong depression of insect growth for resistant and susceptible bean accessions alike. These factors should also be taken into account in breeding for multigenic, durable resistance, in order to exploit the synergism between general and specific resistance factors.