This study is designed to compare the eradication rates，safety and compliance of tailored therapy to those of standard triple therapy in children with H. pylori infection. The primary purpose is to compare the eradication rates of children with H. pylori infection treated with tailored therapy to those treated with standard triple therapy. The secondary purpose is to evaluate the safety, compliance and factors that might affect eradication rates.

Between March 2014 and March 2016, 200 children with upper gastrointestinal symptoms (4-18 years) and H. pylori infection will be recruited at Beijing Children Hospital.After the informed consents are obtained from the guardians, the children will be randomly classified into the two group: 10 days standard triple therapy (Omeprazole 0.8-1.0mg/kg.d,bid, Amoxicillin 30-50mg/kg.d bid， Clarithromycin 15-20mg/kg.d bid), or 10 days tailored therapy including one Proton Pump Inhibitor ( Rabeprazole 0.4-0.5mg/kg.d,bid. or Esomeprazole 0.8-1.0mg/kg.d,bid) and two antibiotics (Amoxicillin 30-50mg/kg.d bid, Clarithromycin 15-20mg/kg.d bid, Metronidazole15-20mg/kg.d bid) based on antibiotics susceptibility and cytochrome P450 isoenzyme 2C19 genotype. Eradication status will be reassessed in four weeks after treatment.

Inclusion Criteria:

• Clinical diagnosis of H. pylori infection.
• Presence of upper gastrointestinal symptoms.
• Referred for upper endoscopy at Beijing Children's Hospital

Exclusion Criteria:

• Presence of endoscopy contraindications
• The administration of any drug that could influence the study results including proton pump inhibitors, H2-receptor blockers, bismuth salts and antibiotics within the previous four weeks;
• Gastrointestinal malignancy;
• Previous gastric or esophageal surgery;
• Severe concomitant diseases
• History of allergy to any of the study drugs;