BACKGROUND: Long-term acid suppression is believed to accelerate atrophic gastritis in Helicobacter pylori-positive patients. The influence of long-term therapy with lansoprazole has not been examined. AIM: To study the clinical and endoscopic efficacy and histological evolution of gastric mucosa during 5 years of maintenance treatment with lansoprazole, 30 mg. METHODS: Seventy-eight patients with endoscopically proven oesophagitis were followed for 5 years. Biopsies taken at the start of the study, during follow-up and after 5 years were available for 73 patients. RESULTS: The total endoscopic relapse rate was 14.1%. At the start of the study, 34 patients were Helicobacter pylori negative and 39 were Helicobacter pylori positive (two atrophy, 25 antral gastritis, 12 pangastritis). At 5 years, no histological changes had occurred in Helicobacter pylori-negative patients. In the Helicobacter pylori-positive group, 20 patients developed pangastritis, six had normal histology and one had antral gastritis. Ten of the 12 patients with pangastritis had reduced antral activity. There was no increase in intestinal metaplasia, but there was a tendency towards regression of atrophy in the antrum and towards increased atrophy in the body of the stomach. CONCLUSIONS: Maintenance treatment with lansoprazole, 30 mg, is efficacious. The development of glandular atrophy and intestinal metaplasia was not accelerated in Helicobacter pylori-positive patients. Helicobacter pylori eradication must be considered only because of the higher cancer risk associated with chronic Helicobacter pylori-related gastritis.