Summary of Trial Design.Lengthy exposure to quinolone-containing triple therapy in Helicobacter pylori eradication leads to the development of drug resistance. Sequential therapy with a quinolone and metronidazole -containing regimen appears to be an effective treatment option. This randomized controlled trial aimed to compare the efficacy of 5-plus 5 days' levofloxacin and metronidazole-containing sequential therapy (EALM) with that of 10-day levofloxacin-containing triple therapy (EAL) in second-line H pylori eradication treatment.One hundred and sixty-four patients who had failed the H pylori eradication attempts using the standard triple therapy (proton pump inhibitor bid, clarithromycin 500 mg bid, amoxicillin 1 g bid × 7 days) were randomly assigned to either an EALM therapy group (n = 82; esomeprazole 40 mg bid and amoxicillin 1 g bid for 5 days, followed by esomeprazole 40 mg bid, levofloxacin 500 mg qd, and metronidazole 500 mg tid, for 5 days) or a 10-day EAL therapy group (n = 82; levofloxacin 500 mg qd, amoxicillin 1 g bid, and esomeprazole 40 mg bid). One patient was lost to follow-up in each group. Follow-up for H pylori status was performed 4 to 8 weeks later.Eradication rates for the EALM and EAL groups were 90.2% (74/82, 95% confidence interval [CI] = 83.7%-96.8%) and 80.5% (66/82, 95% CI = 71.7%-89.2%, P = 0.077) in the intention-to-treat analysis; and 91.4% (74/81, 95% CI = 85.1%-97.6%) and 81.5% (66/81, 95% CI = 72.8%-90.1%, P = 0.067) in the per-protocol analysis. The adverse events for the EALM and EAL groups were 23.5% versus 11.1%, P = 0.038 but were all very mild and were well tolerated except for 1 patient with poor compliance. The compliances were 98.8% and 100%, respectively, between the 2 groups. An antibiotic resistance to levofloxacin was the clinical factor influencing the efficacy of H. pylori eradication therapy in the EAL group, and dual resistance to levofloxacin and metronidazole in the EALM group.Levofloxacin and metronidazole-containing sequential therapy achieved a >90% eradication rate as a second-line H pylori therapy. Dual antibiotic resistance to levofloxacin and metronidazole was the clinical factor influencing the efficacy of H pylori eradication therapy in the sequential therapy (ClinicalTrials.gov number: NCT02596620).