The experimental production of gastric ulcers in dogs by subnucosal injection of ulcerogeic agents is described. The most satisfactory agent tested was 95% ethanol, because it produced immediate changes in the mucosa which delineated the size of the ulcer. The depth of ulceration could be controlled and the ulcer healed readily. Using this technique of ulcer formation, treatment of protuberant gastric lesions was attempted. Eradication of the pedunculated and narrow-based polyps in stomach was almost totally successful by injection into the base. Wide-based lesions, including atypical hyperplasia and the elevated type of early gastric cancer, were also completely eradicated in 96% of the treated cases. There have been no complications. An initial assessment of the practicality of this method in poor risk patients is presented.