The purpose of this study was to determine whether Helicobacter pylori infection and mucosal inflammation result in gastric atrophy in Japanese children. A total of 196 patients ages 1-16 years were retrospectively studied: 131 patients were infected with H. pylori and 65 patients were uninfected. Antral (n = 196) and corpus biopsy specimens (n = 70) were investigated based on the Updated Sydney system. In both the antrum and corpus, H. pylori-infected patients showed significantly higher degrees of inflammation and activity of gastritis, compared with noninfected patients. The prevalence of grade 2 or 3 atrophy in the antrum was 10.7%in H. pylori-infected patients and 0%in the noninfected patients (P < .01) and in corpus 4.3%and 0%, respectively (P = .20). The frequency of intestinal metaplasia in the 2 study groups was 4.6%and 4.6%in the antrum and 0%and 4.2%in the corpus, respectively. Among H. pylori-infected patients, the antrum showed significantly higher degrees of H. pylori density, inflammation and activity of gastritis, and atrophy than the corpus. In the antrum, atrophy was significantly correlated with activity, whereas in the corpus, atrophy correlated with H. pylori density, inflammation, and activity. H. pylori-induced gastric inflammation can cause atrophy in Japanese children, predominantly in the antrum. It remains to be determined whether H. pylori-infected children with gastric atrophy are at increased risk for gastric cancer. The purpose of this study was to determine whether Helicobacter pylori infection and mucosal inflammation result in gastric atrophy in Japanese children. A total of 196 patients ages 1-16 years were retrospectively studied: 131 patients were infected with H. pylori and 65 patients were uninfected In both the antrum and corpus, H. pylori-infected patients showed significantly higher degrees of inflammation and activity of gastritis, compared with those of corpus biopsy (n = 70) with noninfected patients. The prevalence of grade 2 or 3 atrophy in the antrum was 10.7% in H. pylori-infected patients and 0% in the noninfected patients (P <.01) and in corpus 4.3% and 0% respectively (P = .20). The frequency of intestinal metaplasia in the study group was 4.6% and 4.6% in the antrum and 0% and 4.2% in the corpus, respectively. Among H. pylori-infected patients, the antrum shows significantly higher degrees of H. pylori den sity, inflammation and activity of gastritis, and atrophy than the corpus. In the antrum, atrophy was significantly correlated with activity, whereas in the corpus, atrophy correlated with H. pylori density, inflammation, and activity. can cause atrophy in Japanese children, predominantly in the antrum. It remains to be determined whether H. pylori-infected children with gastric atrophy are at increased risk for gastric cancer.