Helicobacter pylori (HP) play an important role in the pathogenesis of chronic gastritis, peptic ulcer diseases as well as gastric cancer. Helicobacter pylori eradication is a critical strategy to reduce aforementioned conditions. Proton-pump inhibitor (PPI)-based triple therapy (Standard dose PPIs+ Clarithromycin 1g/D + Amoxycillin 2g/D or Metronidazole 800 mg/D) is recommended as a frontline treatment in current guidelines for HP eradication, both from Thai and Second Asia-Pacific Consensus Guideline for H.pylori 2009. Unfortunately, it has been reported an unacceptably low eradication rate (<85%) of this regimen in a tertiary care hospital in Thailand. This occurrence is not surprised as the worldwide efficacy of this regimen had decreased to 50-75%. Of this, Clarithromycin resistance has been a major cause of the treatment failure.