The effect of protein fractions isolated from cereal grains on the development and survival of the bean weevil, Callosobruchus maculatus, was investigated using wheat, rice and maize. These cereals were fractionated into albumins, globulins, prolamins, glutelins and a residue. The fractions were incorporated in artificial seeds which were infested by C. maculatus. Survival (as indicated by LD50) and development (as indicated by WD50) of 20-day-larvae of the bruchid were negatively affected by most of the fractions. Rice globulins were the most detrimental and affected both the survival and development of the larvae, while wheat albumins and globulins had a stronger effect on larval development than on survival. A previously isolated maize α-amylase/trypsin inhibitor showed an LD50 of 1.5% to Callosobruchus maculatus.