Background/Aims: The aim of this study was to investigate the differences in the frequency of intestinal metaplasia, its subtypes, and serum pepsinogen levels between Helicobacter pylori (H. pylori)-infected patients with duodenal ulcer and patients with chronic gastritis. Methods: We evaluated the area of atrophic change, frequency of intestinal metaplasia and subtypes, serum pepsinogen (PG) levels, and seropositivity of CagA and VacA in 25 H. pylori-infected patients with duodenal ulcer and 25 patients with chronic gastritis. Results: Eight percent of patients with duodenal ulcer showed open type, whereas 52% of patients with chronic gastritis showed it (p=0.001). The intestinal metaplasia was less frequently observed in patients with duodenal ulcer (36% vs. 68%, p<0.005). However, there was no difference in frequency of intestinal metaplasia subtypes between the two groups. The patients with duodenal ulcer showed significantly high serum PG I/II ratio (3.3±1.1 vs. 2.2±0.8, p<0.001). There was no difference in the seropositivity of CagA and VacA between the two groups. Conclusions: H. pylori-infected patients with duodenal ulcer have the significantly smaller area of atrophic change and lower frequency of intestinal metaplasia than patients with chronic gastritis. Serum PG I/II ratio which is significantly high in patients with duodenal ulcer reflects the degree of the atrophic change of the gastric mucosa, but CagA and VacA do not. (Kor J Gastroenterol 2000;36:155 - 162)