Objectives To investigate the relationship between H.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 H.pylori eradication in H.pylori-positive subjects in a high incidence region of gastric cancer. Methods One thousand and six adults were selected from the general population in Yantai, Shandong province, a high incidence region for gastric cancer in China. Gastroscopy and Campylobacter-like organism (CLO) testing were performed on all subjects. Biopsy samples from the gastric antrum and body were obtained for histology and assessment of H.pylori infection. All H.pylori-positive subjects were then randomly divided into two groups: treatment group receiving Omeprazole Amoxicillin Clarythromycin (OAC) triple therapy and placebo as controls. These subjects were endoscopically followed up in the second and fifth year. We compared the endoscopic appearance and histology of the biopsy specimens from the same site obtained at the first and last visits. Conclusions H.pylori eradication results in remarkable reduction in the severity and activity of chronic gastritis, marked resolution of intestinal metaplasia in the antrum. On the other hand, continuous H.pylori infection leads to progressive aggravation of atrophy and intestinal metaplasia.