Established risk factors for gastric cancer include a diet high in nitrate or nitrite and low in vitamin C and the presence of achlorhydria or hypochlorhydria. The aim of this study was to investigate the relationship between intragastric nitrite concentration and atrophic change of the stomach or gastric carcinogenesis in Japanese Helicobacter pylori-infected patients. Gastric juice pH, nitrite, and total vitamin C concentrations in gastric juice, serum pepsinogen I and II concentrations, and specific Helicobacter pylori antibody were analyzed. Intragastric total vitamin C concentration was decreased by Helicobacter pylori infection of the gastric mucosa and with progression of the atrophic grade. There was a significant positive correlation between atrophic grade and intragastric nitrite concentration. In conclusion, the levels of nitrite in gastric juice play a causal role in the development of cancer in Helicobacter pylori-associated atrophic gastric mucosa.