It has been reported that the stimulating effect of insulin-induced hypoglycemia influencing the gastric secretion passes through two pathways, the vagus and the hypothalamic-pituitary-adrenal system. Gastric analysis by insulin hypoglycemia was performed in an attempt to obtain an acid secretory pattern for gastric and duodenal ulcers. Insulin used was 10 units of Novo regular insulin. In duodenal ulcer, nearly the same data as reported by Stempien and his associates were obtained. In gastric ulcer, however, many cases showed delayed gastric secretion, which was described to be due to hypothalamic-pituitary-adrenal system, as compared to the patterns in duodenal ulcer and normal healthy control. This suggested that the hypothalamic-pituitary-adrenal system played an important role in the etiology of gastric ulcer. It was suggested that the increased excitation of two regulating mechanisms, the vagal center and the hypothalamic-pituitary-adrenal system, acted as the principal role in the etiology of duodenal ulcer.