Objectives To investigate the relationship between H1 pylori infection, gastric cancer and other gastric diseases through the changes in gastric mucosa and the status of different gastric diseases within 5 years after H1 pylori eradication in H1 pylori-positive subject s in a high incidence region of gastric cancer1 Methods One thousand and six adults were selected from the general population in Yantai, Shandong province, a high incidence region for gastric cancer in China1 Gastro scopy and Campylobacter2like organism (CLO) testing were performed on all subject s1 Biopsy sample s from the gastric antrum and body were obtained for histology and as sessment of H1 pylori infection1 All H1 pylori2po sitive subject s were then randomly divided into two group s: treatment group receiving Omeprazole Amoxicillin Clarythromycin (OAC) triple therapy and placebo a s controls1 The se subject s were endo scopically followed up in the second and fifth year1 We compared the endo scopic appearance and histology of the biop sy specimens from the same site obtained at the first and la st visit s1 Re s ult s All 552 H1 pylori2po sitive subject s were randomly and evenly divided into treatment group or control group1 During the five2year follow2up, the numbers of patient s who continued to be negative or po sitive for H1 pylori were 161 and 198, re spectively1 Statistical analysis revealed that : ①At the initial visit, there were no significant difference s in the severity and activity of inflammation, atrophy and inte stinal metapla sia between the biop sy specimens from the antrum and body re spectively in both group s1 ② The severity and activity of inflammation in both the antrum and body were markedly reduced after H1 pylori eradication (P=01000) 1 ③Within five years after H1 pylori eradication, inte stinal metapla sia in the antrum either regre s sed or had no progre s sion, while the proportion of inte stinal metapla sia in the H1 pylori2po sitive group increa sed significantly (P=01032) 1 ④After H1 pylori eradication, the atrophy in both the antrum and body had no significant regre s sion1 The P value wa s 01223 and 01402, re spectively1 Co nclus io ns H1 pylori eradication re sult s in remarkable reduction in the severity and activity of chronic ga stritis, marked re solution of inte stinal metapla sia in the antrum1 On the other hand, continuous H1 pylori infection leads to progre s sive aggravation of atrophy and inte stinal metapla sia1