Background and objective: To investigate the presence of any possible association between H. pylori density in the stomach and the efficacy of triple (lansoprazole 30mg b.i.d., clarithromycin 500mg b.i.d. and amoxicillin 1g b.i.d. for 14 days) and bismuth-containing quadruple (colloidal bismuth subcitrate 300mg q.i.d., lansoprazole 30mg b.i.d., tetracycline 500mg q.i.d. and metronidazole 500mg t.i.d. for 14 days) eradication therapies.