The partial replacement of the human duodenal mucosa by epithelial cells containing gastric-type mucus(gastric metaplasia) is not an uncommon finding, and an emphasis on its etiological role in duodenal ulcerogenesis has been proposed. It is unclear, Furthermore, all the previous studies were done with endoscopic biopsy specimens. We reviewed a total of 118 surgically resected stomachs with attached duodenal stumps(24 cases of gastric ulcer, 15 duodenal ulcer and 79 advanced gastric cancer). The gastric-type mucous cells were homogeneously stained red with PAS in contrast to the intestinal cells which gave a strong PAS stainability only along the the brush border. The gastric metaplasia was seen near the tips or on the sides of the villi and occasionally in the crypts. It was observed in 8 cases(53%) in duodenal ulcer, 12 cases(50%) in gastric ulcer and 29 cases(37%) in gastric cancer. There were no significant statistical differences in incidence among the groups. Nevertheless, diffuse form of gastric metaplasia was more prevalent in patients with duodenal ulcer(p<0.05).