SUMMARYBackground: The optimal treatment of patients with Helicobacter pylori resistant to metronidazole has not been established. Aim: To compare the efficacy of quadruple and furazolidone-based triple therapy in the eradication of H. pylori resistant to metronidazole. Methods: Duodenal ulcer patients (n ¼ 70) in whom initial eradication therapy failed and who harboured H. pylori strains resistant to metronidazole were randomized to receive one of the following 7-day regimens: colloidal bismuth subcitrate, 240 mg, tetracycline, 750 mg, and furazolidone, 200 mg, each given twice daily (BTF), or omeprazole, 20 mg b.d., colloidal bismuth subcitrate, 240 mg b.d., tetracycline, 500 mg q.d.s., and metronidazole, 500 mg b.d. (OBTM). H. pylori status was assessed by culture, histology and rapid