Résumé : The present experiments were designed to compare the effects of streptozotocin and 1-methyl-1-nitrosourea upon glucose-induced insulin secretion by isolated islets of Langerhans. Both drugs depressed the insulin response at one and two hours incubation but higher molar concentrations of the nitrosourea were required to produce the same level of inhibition as streptozotocin, a difference perhaps related to the latter's glucose moiety.