Some benefit was found from a diet of milk alone and from the use of a duodenal extract in the prophylactic treatment of peptic ulcers produced experimentally by the administration of cinchophen. Mucin appeared to be definitely beneficial in some cases but in others a chronic ulcer developed similar to those found in control animals fed cinchophen without prophylactic treatment. A chronic lesion was not produced in the presence of alkali-milk diet therapy. No benefit was observed from intramuscular injections of histidine monohydrochloride.