A prepn. consisting of a total parietal cell pouch drained by an isoperistaltic jejunal fistula into the 2d portion of the duodenum has been evaluated for its ulcer producing capacity in the dog. When the vagus nerves were intact to the pouch, and the antrum was in contact with food, 15 of 16 dogs (94%) died with ulcers an avg. of 3 weeks after operation. Removal of the antrum affords more protection than vagus section but less than these 2 procedures combined. Dogs protected against ulcer development survive in good nutritional condition.