Background/Aims: Proton pump inhibitor-based triple therapy is recommended as the first-line treatment for Helicobacter pylori (H. pylori) eradication. We compared the efficacy of two different regimens of triple therapy in patients with H. pylori-associated duodenal ulcer. Methods: Forty-one patients were prospectively randomized to receive either regimen OCA (omeprazole 20 mg, clarithromycin 500 mg, amoxicillin 1 g, all twice daily) or OCM (omeprazole 20 mg, clarithromycin 500 mg, metronidazole 500 mg, all twice daily) for one week. H. pylori infection was confirmed by CLO testTM, histology (Giemsa stain) and culture at the beginning of this study. H. pylori eradication was defined as an absence of H. pylori infection on histology (two antral and two corpus) and culture (two antral and two corpus) four weeks after the completion of therapy. Results: The overall eradication rate of two regimens was 65.9%. H. pylori eradication rate was 57.1% in the group of OCA and 75.0% in the group of OCM. Patient's sex, age, smoking status, alcohol consumption, or history of ulcer had no significant effect on the eradication of H. pylori. Conclusions: Both one-week OCA and OCM therapy resulted in relatively low eradication rates. No difference was found in H. pylori eradication efficacy between OCA and OCM regimens. Thus, further studies focusing on the treatment period may be required. (Kor J Gastroenterol 2000;35:16 - 22)