This prospective study was to assess the efficacy of nonbismuth containing quadruple therapy as first-line H. pylori treatment and to determine the clinical factors influencing patient outcome. We enrolled 200 H. pylori-infected naïve patients. They were prescribed either a 7-day nonbismuth containing quadruple therapy group (EACM, esomeprazole 40 mg twice daily, amoxicillin 1 g twice daily, metronidazole 500 mg twice daily, and clarithromycin 500 mg twice daily) or a 7-day standard triple therapy group (EAC, esomeprazole 40 mg twice daily, amoxicillin 1 g twice daily, and clarithromycin 500 mg twice daily). Follow-up studies to assess treatment responses were carried out 8 weeks later. The eradication rates attained by EACM and EAC groups were 95.6% (95% confidence interval [CI] = 89.4%-98.3%) and 79.3% (95% CI = 70%-86.4%) in the per-protocol analysis (P < 0.001) and 88% (95% CI = 80.2%-93.0%) and 73% (95% I = 63.6%-80.3%) in the intention-to-treat analysis (P = 0.007). Clarithromycin resistance, metronidazole resistance, and dual clarithromycin and metronidazole resistances were the clinical factors influencing H. pylori eradication in EACM group. Clarithromycin resistance and dual clarithromycin and metronidazole resistances were the influential factor for EAC treatment. In conclusion, the results suggest that 7-day nonbismuth containing quadruple therapy could achieve a grade "A" report card for first-line H. pylori treatment.