This study was performed to assess the clinical therapeutic effectiveness of anti-histamine agent, ranitidine. The drug was given in the dose of 150mg twice a day to 12 cases of gastric ulcer and 11 cases of duodenal ulcer. Initial diagnosis and follow up observation after 4 weeks, 6 weeks and 8 weeks of treatment were made by the upper G-I endoscopy. The results observed are as followings. 1) The male to female ratio of the subject was about 20:3 and the most prevalent age group was the sixth decade of the life in both the gastric and duodenal ulcer groups. 2) The location of gastric ulcer were 7 cases in body and 5 cases in angle of the stomach and duodenal ulcer were 7 cases in bulb and 4 cases in pyloric area. 3) As for the subjective symptoms, epigastric pain, heart-burning sensation, hunger pain, abdominal discomfort, dyspepsia were experienced, and were relieved after 1 week of treatment in 60 80%, and were completely relieved after 4 weeks of treatment in all cases respecti vely. 4) The cumulative rates of complete healing of the gastric ulcer (12 cases) were 75% (9 cases) after 4 week, 92% (11 cases) after 6weeks, 100%(12 cases) after 8 weeks of treatment, and those of the duodenal ulcer (11 cases) were 91%(10 cases) after 4 weeks, 100%(11 cases) after 6 weeks of treatment. 5) The untoward side effect were not found. In conclusion ranitidine appears to be effective and safe for the treatment of patients with peptic ulcer disease.