The neutrophilic infiltration has been regarded to represent the activity of Helicobacter pylori gastritis. It may involve the epithelium and/or lamina propria. The incidence and degree of the two types of infiltration do not correlate with each other frequently. We correlated the two types of neutrophilic infiltration with H. pylori infection and other pathologic parameters respectively in 300 randomly selected gastric biopsies as well as serial biopsies from a separate group of 95 patients who were treated for H. pylori infection. The "random biopsies" had chronic gastritis of various degrees, and the organisms were identified in 239 cases (79.7%); in the "treated group," the organisms disappeared completely in 62 cases (65.3%). Characteristically, the intraepithelial neutrophilic infiltration was predominantly localized to the proliferative zone of the gastric mucosa (zone 2) where the density of H. pylori was considerably lower than the surface epithelium. In the "random biopsies," both acute epithelial and interstitial neutrophilic infiltration correlated significantly (p < 0.01) with the H. pylori infection. In the "treated group," however, only acute epithelial inflammation correlated significantly (p < 0.01) with the eradication of infection while acute interstitial inflammation did not. Acute epithelial inflammation was no less frequently present in advanced chronic gastritis than in early chronic gastritis. Acute epithelial inflammation of the proliferative zone is a characteristic pathologic finding of H. pylori gastritis, and appears to be directly associated with the pathogenesis of H. pylori gastritis and its progression.