The prevalence of antral intestinal metaplasia (IM) in underlying Helicobacter pylori (HP) gastritis was studied in biopsy specimens of the antral mucosa obtained from 2,692 patients with histologically proven HP gastritis. The prevalence of IM varied in the groups investigated: 47.4% in gastric ulcers, 30.5% in pyloric ulcers, 16.8% in duodenal ulcers, 21.8% in gastritis with no lesions and 9.8% in chronic antral erosions (p < 0.001). A hypothetical model for the role of HP in the development of IM is presented: HP probably promotes mucosal regeneration. The prolonged stimulatory effect on regeneration could then, in the course of time, lead to an increasing likelihood of IM developing.