Bombesin (BBS) has been shown to promote pancreatic growth as well as the development of pancreatic (pre)neoplasia in rats. The present study was carried out to determine the effects of bombesin on pancreatic growth and on the development of pancreatic (pre)neoplastic lesions in hamsters treated with N-nitrosobis(2-oxopropyl)amine (BOP). Bombesin caused an increase in growth of the pancreas accompanied by a decrease in the number of (pre)neoplastic ductular pancreatic lesions. Lorglumide (CR-1409) did not influence these effects of bombesin. It is concluded that in BOP-treated hamsters the effect of bombesin on the pancreas is not mediated by cholecystokinin (CCK). These data support the existence of species difference between rats and hamsters with regard to the effect of bombesin on pancreatic carcinogenesis.