Background/Aims: Bismuth-based quadruple therapy for second-line eradication treatment achieves the eradication rate ranging from 70% to 81% due to antimicrobial resistance and poor compliance. The aim of this study was to compare the eradication rate of levofloxacin-based triple therapy with that of bismuth-based quadruple therapy in second-line Helicobacter pylori (H. pylori) eradication therapy. Methods: Seventy-six outpatients with persistent H. pylori infection after first-line triple therapy were enrolled in this prospective randomized trial. The subjects were randomized to receive levofloxacin 300 mg, amoxicillin 1 g, and pantoprazole 20 mg, given twice daily for 7 days (LAP group), or metronidazole 500 mg twice, tetracycline 500 mg four times, and pantoprazole 20 mg twice, bismuth subcitrate 600 mg twice daily for 7 days (MTPB group). Eradication was confirmed with 13C-urea breath test or rapid urease test 4 weeks after the cessation of therapy. Results: Among Seventy-six patients initially included, eleven were lost during follow-up. The eradication rates, expressed as intention to treat (ITT) and per protocol (PP) analyses, were 51.6% and 53.3% in the LAP group, and 48.9% and 62.9% in the MTPB group, respectively. There was no significant difference in H. pylori eradication rates between the two groups (p=0.815 by ITT, p=0.437 by PP). LAP regimen was better tolerated than MTPB regimen with lower incidence of side effects (10.0% versus 31.4%, p=0.03). Conclusions: H. pylori eradication rates of levofloxacin-based triple therapy and bismuth-based quadruple therapy were not significantly different in second-line H. pylori eradication therapy, and low incidence of side effects was observed in levofloxacin-based triple therapy. (Korean J Gastroenterol 2008;51:285-290)