We studied the relationship between Helicobacter pylori (H. pylori) infection and gastric acid secretion, along with fasting serum gastrin levels, in 55 asymptomatic healthy volunteers under 30 years old (29 H. pyloripositive, 26 H. pylori-negative). Mean scores of antral gastritis were significantly higher in H. pylori-positive subjects than in H. pylori-negative subjects. There was no significant difference in both basal and maximal acid output between H. pylori-positive and H. pylori-negative subjects. Fasting serum gastrin levels were significantly higher in H. pylori-positive subjects than in H. pylorinegative subjects. Sex did not significantly affect gastritis scores, gastric acid secretion, or fasting serum gastrin levels, although maximal acid output was slightly higher in H. pylori-negative men than in H. pylori-positive men. Our results suggest that H. pylori infection has no direct effect on gastric acid secretion in young healthy subjects, although it induces hypergastrinemia.