Plasma gastrin and gastric acid responses to intravenous injection of insulin (0.2 IU/kg) were measured in 8 patients with Chagas' disease, which is known to be associated with extensive reduction of the intramural neurons of the digestive tract, and in 6 control subjects. All subjects developed hunger, sweating and tachycardia, and exhibited less than 50 mg/dl venous blood glucose. Plasma gastrin responses in Chagas' disease patients (median: 3.60 nmol L-1 min-1; range: 1:12 to 10.60 nmol L-1 min-1) were significantly higher than for control subjects (median: 0.52 nmol L-1 min-1; range: 0.25 to 1.09 nmol L-1 min-1). Gastric acid output was significantly lower in Chagas' disease patients (median: 3.5 mmol/h; range: 2.1 to 13.6 mmol/h) than in controls (median: 30.3 mmol/h; range: 7.3 to 38.2 mmol/h). These data show that chagasic patients have abnormally high gastrin release and low gastric acid secretion in response to insulin, and thus indicate that loss of intrinsic innervation of the stomach does not abolish the gastrin response to insulin hypoglycemia.