After evaluating more than 6000 accessions from the genebank for resistance to the common boll weevil of Z. subfasciatus and more than 1000 accessions for resistance to Acanthoscelides obtectus in the period 1975 to 1981, it was concluded that the levels of resistance in the cultivated materials are too low to be of economic importance. However, in 1981 evaluations of 206 semicultivated bean accessions previously collected in Mexico showed that some were highly resistant to both weevil species. This resistance was found to be expressed in a considerable reduction in the number of weevil progeny, together with a delay in their development and dry weight. The most promising of the resistant lines was incorporated into the crossing program in an attempt to transfer the resistance genes to commercial materials. Successful results will be a major breakthrough in the control of stored grain insects. CIAT Report 1992, pp 18.