Blood glucose and insulin responses to intravenous glucose 500 mg/kg in a group of alcoholic chagasic patients (Group I, N = 15) were assessed and compared to those of a group of patients with Chagas' disease without alcoholism (Group II, N = 16), a group of alcoholics without Chagas' disease (Group III, N = 22), and a group of non-alcoholics without Chagas' disease (Group IV, N = 15). Determinations of serum glucose and insulin were done under fasting conditions, 5 and 10 min after the injection of 50% glucose. There was no difference in mean serum glucose levels between groups. Mean serum insulin levels at times 5 and 10 min and for the total integrated response were lower (P < 0.05) in Groups I and II as compared to Group IV; at time 10 min the mean was lower (P < 0.05) in Group III as compared to Group IV. There was a nonsignificant trend for a lower insulinemic response in Group I as compared to Group II. These data suggest denervation of or injury to pancreatic B cell by Chagas' disease.