AIM: 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. METHODS: 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. RESULTS: The mean gastric H+/K+-ATPase activity in Hpylori-positive group (42 patients) was slightly higher than that in Hpylori-negative group (29 patients) (169.65±52.9 and 161.38±43.85nmol P/(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 P/(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 vs75.04±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). CONCLUSION: Gastric H+/K+-ATPase activities are not associated with H pylori status in patients with chronic gastritis. AIM: 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. METHODS: 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 RESULTS: The mean gastric H + / K + -ATPase activity in Hpylori-positive group (42 patients were slightly higher than that in Hpylori-negative group (29 patients) (169.65 ± 52.9 and 161.38 ± 43.85 nmol P / (mg · h), respectively, P = 0.301). After eradication of H pyl ori, the gastric H + / K + -ATPase activities slightly decreased compared to prior therapy (165.03 ± 59.50 and 158.42 ± 38.93 nmol P / (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) CONCLUSION: Gastric H + / K + -ATPase activities are not associated with H pylori status in patients with chronic gastritis.