The role of Helicobacter pylori (H pylori) infection in gastric acid secretion of patients with chronic gastritis remains controversial. This study was designed to elucidate the effect of H pylori on H+/K+-ATPase activities in gastric biopsy specimens.Eighty-two patients with chronic gastritis who had undergone upper endoscopy were included in this study. H pylori infection was confirmed by rapid urease test and histology. Gastric H+/K+-ATPase activities and serum gastrin concentrations were measured by an enzymatic method and radioimmunoassay, respectively. For those patients who received triple therapy for eradicating H pylori, changes in the activity of gastric H+/K+-ATPase and serum gastrin levels were also measured.The mean gastric H+/K+-ATPase activity in H pylori-positive group (42 patients) was slightly higher than that in H pylori-negative group (29 patients) (169.65+/-52.9 and 161.38+/-43.85 nmol Pi/(mg.h), respectively, P=0.301). After eradication of H pylori, the gastric H+/K+-ATPase activities slightly decreased compared to prior therapy (165.03+/-59.50 and 158.42+/-38.93 nmol Pi/(mg.h), respectively, P=0.805). The mean basal gastrin concentration was slightly higher in H pylori-positive patients than in H pylori-negative patients (87.92+/-39.65 pg/mL vs 75.04+/-42.57 pg/mL, P=0.228). The gastrin levels fell significantly after the eradication of H pylori. (Before treatment 87.00+/-30.78 pg/mL, after treatment 64.73+/-18.96 pg/mL, P=0.015).Gastric H+/K+-ATPase activities are not associated with H pylori status in patients with chronic gastritis.