Ulcer induced by adrenalectomy has been found in close relationships with abnormalities in blood components, particularly with inbalance in serum K and Na. When the abnormality of these blood components after adrenalectomy was corrected by oral administration of 1.0% NaCl solution, by substitution therapy utilizing adrenal cortical hormone (cortisone) or by vagotomy, ulcer could be prevented. However, the excessive substitution therapy was found to fail preventing the induction of ulcer, intramuscular administration of cortisone 5 mg/animal/day had failed to prevent the ulcer. But a formation of ulcer in adults rats could be prevented by oral administration of 1 % KCl with cortisone 5 mg/animal/day after adrenalectomy. Since the facts descrived above, it was concluded that inbalance of the blood components due to disharmony in adrenal cortical hormones resulted in weakening of the tissue resistance of gastric mucosa, which would be one of the most important factors in experimental gastric ulcer mentioned above. In this meaning, 1 called it as "gastric ulcer due to hormonal disharmony" and discussed in detail.