The recurrence rate of duodenal ulcer(DU) within 12 months after treatment has been re- duced to 0-27% with eradication of Helicobacter pylori(H. pylori) from 50-90% without eradi- cation. This study was conducted to find the ideal method of treatment in the aspects of erad- ication of H. pylori, symptom reduction, and side effect among the three treatment methods. This study was performed for 73 patients with DU, and four different methods, for identifying H. Pylori infection-Gram stain of touch print, culture, H&E stain, CLO test-were taken just be- fore treatment and taken 4 weeks later after the completion of ulcer therapy to find the eradi- cation rate of H. pylori in three treatment groups. The first treatment group consisted of col- loidal bismuth subcitrate(CBS) 240mg twice a day, metronidazole 250mg thrice, and amoxicillin 500mg thrice for 6 weeks(Group I, n=28), the second group omeprazole 20mg once a day for 6 weeks and amoxicillin 500mg thrice for the first two weeks(Group II, n=l3), and the third group ranitidine 150mg twice a day or omeprazole 20mg once for 4 weeks and thereafter CBS 120mg four times a day, metronidazole 500mg thrice and amoxicillin 500mg four times for 2 weeks(Group III, n=32). The degree of symptom reduction and frequency of side effect in each treatment group were evaluated during the treatment period. The eradication rate of H. pylori was 89.3% in Group I, 23.1% in Group II, and 87.5% in Group Ill, In Group I, more than 50% of symptom reduction within 1 week was 55.6%, within 2 weeks 22.2% and after 2 weeks 22.2%; in Group II, more than 50% of symptom reduction within 1 week was 100%; in Group III, the same rate of reduction within 1 week was 96.6% and within 2 weeks 3.4%. The frequency of side effect in Group I was 21.2% including 5 patients (15.2%) in whom the medication could not be completed due to major side effect; the frequen- cy of side effect in Group II was 0%; that in Group lIl was 21.9/, in all of whom the side effect was minor so the medication could be completed. From these results, we concluded that in the aspect of eradication of H. pylori, the triple therapies for 6 or 2 weeks(Group I and Ill) are better than omeprazole and amoxicillin therapy(Group II), and in the aspect of symptom reduction, the triple therapy for 2 weeks after ranitidine or omeprazole for 4 weeks(Group Ill) is better than the triple therapy for 6 weeks (Grup I ). (Korean J Gastroenterol 1994; 26: 47 55)