Although a strong association has been established between chronic Helicobacter pylori infection and peptic ulcers, the role of H. pylori is not necessarily causative because there are many patients infected with H. pylori who do not develop peptic ulcer. Therefore, we studied the relationship between the gastric mucosal environment and the development of peptic ulcers. We examined 165 endoscopic biopsy specimens from the gastric mucosa of 33 patients with peptic ulcers using the 5-point gastric biopsy method. The follow-up biopsies done within 3 weeks were well correlated with the first biopsy samples. We also reviewed the clinicohistopathological findings of 2250 endoscopic biopsy specimens from 450 patients with active gastric and/or duodenal ulcers. Over 90% of the patients with duodenal ulcer, with or without gastric ulcer, had no fundic gland atrophy, and a high incidence of intestinal metaplasia and pyloric mucosal atrophy was found in the patients with gastric ulcer. These findings suggest that patients with concomitant active gastric and duodenal ulcers exhibit severe atrophic changes in the antral mucosa but not in the fundic mucosa.</p