The study was done in the laboratory of Entomology of the Centro de Energia Nuclear na Agricultura (CENA), University of Sao Paulo, in Piracicaba, State of Sao Paulo, Brazil. This research was carried out to observe the effect of irradiated beans (Phaseolus vulgaris, (L.), cultivar Rosinha) on the longevity and prolificity of Zabrotes subfasciatus (Boheman, 1833) (Coleoptera, Bruchidae). The first part of the study included the rearing of five generations of Zabrotes subfasciatus which were fed with irradiated beans (0, 10, 20, 100 e 200 krad, with a dose rate of approximately 70 krad/h). The second one consisted of growth of seven generations on irradiated beans (0, 100, 500, 1500 and 3000 krad, with a dose rate of approximately 70 krad/h). The data were obtained through daily countings of insect birth and death rates. It was concluded that irradiation modified the nutritional quality of beans, affecting the development of Zabrotes subfasciatus. This effect was studied through the longevity and prolificity, which were altered as compared with the control, once they were higher for the dosis of 1500 and 3000 krad. (author).