Gastric cancer is the fourth most common type of cancer and the second leading cause of cancer-related death in the world. In China, more than 390,000 new patients are diagnosed with gastric cancer and more than 300,000 patients are killed by the terrible disease annually. Although gastric cancer has a multifactorial etiology, infection with H. pylori is highly associated with gastric carcinogenesis. Therefore, eradication of H. pylori infection appears to reduce the risk of gastric cancer. However, several recent controlled interventional trials by H. pylori eradication to prevent gastric cancer have yielded disappointing results. The exact effect of H.pylori eradication on prevention of gastric cancer is unclear up to now. To clarify this problem, the investigators conducted a prospective, randomized, double-blind, placebo-controlled, population-based study to determine whether H pylori eradication would reduce the incidence of gastric cancer in a high-risk population in China.

Inclusion Criteria:

• Healthy registered inhabitants from 10 villages in a high-risk county of gastric cancer in China
• Age 30-59 years
• A willingness to participate in the study as indicated by written informed consent

Exclusion Criteria:

• Severe concomitant illness (eg, severe hypertension, coronary heart disease, diabetes mellitus, stroke, asthma, liver cirrhosis, tuberculosis, infectious hepatitis, and cardiac, respiratory, hepatic, or renal insufficiency)
• Patients with epilepsy or severe mental illness
• Previous diagnosis of cancer
• A history of esophageal or gastric surgery
• Drug abuse and drug dependence
• Allergic to omeprazole, amoxicillin, or clarithromycin
• Pregnant and lactating women
• Previous history of H pylori eradication treatment
• A negative 13C-urea breath test (UBT)
• A definite indication of H. pylori eradication (eg, gastric or duodenum ulcer)
• Dysplasia or carcinoma lesions are found in esophageal or gastric histopathological examination
• Other factors or conditions might influence the results of study