Ojo de Cabra bean lectin was partially characterized, and the nutritive value of raw and heat-processed beans were investigated in relation to this compound. The lectin purified by affinity chromatography on immobilized fetuin presented two bands of about 30 kDa in SDS-PAGE. It had an unusual high hemagglutinating capacity, and it was inhibited by fetuin and galactose. The lectin activity decreased 84% by dry heating and 99.8% by cooking. Although biological values of cooked beans were similar to those of other beans, toasting affected the PER and weight of rats, but not the NPR. Raw beans were highly toxic; 33 % of animals died at 10 days. The NPR value was negative, and this group lost more weight than the N-free diet group. The histological examination revealed that the dietary lectin was bound to the mucosal surface coat of the duodenum and jejunum.