摘要AIM: To follow the principles of evidence based medicine to reach the integrated results of these studies.METHODS: Twenty-one papers of case-control studies were selected, including 11 on gastric cancer, 7 on precancerous lesion of stomach and 3 on lymphoma of stomach: Meta analysis was used to sum up the odds ratios (OR) of these studies.RESULTS: H. Pylori vsgastric cancer (intestinal and diffuse type): the odds ratio from the fixed effect model is 3.0016(95% Cl 2.4197-3.7234, P < 0.001 ). H. Pylori vs precancerous lesion of stomach: a random effect model was used to calculate the summary odds ratio and its value is 2.5635 (95% Cl: 1.8477-3.5566, P < 0.01). H. Pylori vs lymphoma of stomach: though the quantity of literature is too small to make Meta analysis, the data of these 3 studies show that lymphoma of stomach is highly associated with H. Pylori infections.CONCLUSION: Since it had been revealed that H. Pylori infection pre-exists in gastric carcinoma and precancerous lesions, the results of Meta analysis present a strong evidence to support the conclusion that H. Pylori infection is a risk factor for gastric carcinoma.