Background: Helicobacter pylori (H. pylori) is an important cause of duodenal ulcer (DU) and eradication this infection can prevent complication related to DU and recurrence of the DU.Quadruple therapy (QT) is one of the recommended treatment regimen for the H. pylori eradication. But there has not been enough data for impact of the QT on eradication success of the H. pylori in patients with DU. We aimed to investigate success of QT in H. pylori positive patients with DU. Method:We included 140 patients who had DU and histology proven H. pylori infection into the study. All patients were given a quadruple therapy program for 14 days consisting of colloidal bismuth substrate 300 mg 2x2; tetracycline hydrochloride 500 mg (qid); metronidazole 500 mg (tid) and a proton pump inhibitor (PPI) (bid) randomly which esomeprazole 20 mg for patients in group 1 (ETMB), lansoprasol 30 mg for group 2 (LTMB), pantoprazole 40 mg for group 3 (PTMB) and rabeprazole 20 mg for group 4 (RTMB). Eradication rate was measured by urea breath test at least 6 weeks after the end of the treatment Results: Average eradication rate was 78.8 % in ITT analysis (%95 CI 0. 71-0. 84) and 81.8% in PP analysis for all groups (% 95 CI 0. 74-0. 87). There was no significant differences between different PPI groups. Conclusion:In patients with DU and H. pylori infection, QT can provide an acceptable but not enough successful eradication success.