Seven hundred seventy biopsy specimens obtained from 10 different sites in stomachs of 77 patients were examined for the presence of active chronic gastritis (ACG) and Helicobacter pylori to investigate the characteristics of gastritis in the antrum and body. Forty-eight patients with ACG at one or more sites were all H. pylori positive. H. pylori was not found in 20 patients who had chronic gastritis with no activity or in 9 patients who had histologically normal mucosa. In patients with ACG in at least one biopsy site, a strong positive topographic association between H. pylori colonization and ACG was seen in the Warthin-Starry stain. The frequency of H. pylori colonization was similar in the antrum and body. However, the incidence of ACG declined significantly proximal to the borderline between the antrum and body (P less than 0.001). The average grade of gastritis at the individual biopsy sites was distributed evenly throughout the antrum but decreased markedly in the body (P less than 0.0001). In the same manner, the average grade of H. pylori colonization decreased in the body (P less than 0.0027). The grade of H. pylori colonization in the individual biopsy specimens was closely related to the grade of gastritis (r = 0.51); also, the grade of neutrophil infiltration was related to the grade of gastritis (r = 0.79). A good correlation existed between the grade of H. pylori colonization and the grade of neutrophil infiltration (r = 0.70). The results of this study show a different expression of H. pylori gastritis in the antrum and body, which is the main subtype of chronic type B gastritis. The close topographic and graded association between the presence of H. pylori and the activity and grade of gastritis lend further support to the major pathogenic role of H. pylori in active chronic gastritis. The different expression of gastritis in antrum and body is suggested to be increased reactivity of the antral mucosa to the infection, possibly on the basis of an enhanced immunologic response to H. pylori in this region.