It is known that cysteamine-induced duodenal ulcers in rats are similar to the human duodenal ulcers in some aspects. We investigated their similarities in view of adrenalin-stimulated gastric acid secretion and gastrin secretion in these rats. Acid outputs decreased in the control group by the administration of adrenaline, but in the cysteamine-administered group acid outputs increased dose dependently. Serum gastrin levels and plasma noradrenaline levels increased by cysteamine administration. The abnormal gastric acid secretion by the adrenalin infusion in the process of cysteamine-induced duodenal ulcers in rats, which was resembled to that of duodenal ulcer patients, was recognized.