The aim of this study is to clarify the relationship between the incidence of atrophic gastritis and Helicobacter pylori infection. A case control study was conducted in 1995. Cases and controls were selected among those who took an annual health examination in a rural area of Fukuoka Prefecture. Cases are those who were not diagnosed as having atrophic gastritis in 1991 or 1992 but were diagnosed as having atrophic gastritis in 1995 by the examination of serum pepsinogens. Controls are those who were not diagnosed as having atrophic gastritis between 1991, or 1992 and 1995. Helicobacter pylori infection was evaluated by anti Helicobacter pylori IgG in 1995. The odds ratio for atrophic gastritis was calculated using Logistic regression analysis. The odds ratio of age and sex was not significant, but the odds ratio of Helicobacter pylori infection was significantly elevated (5.2, 95% confidence interval: 2.08-13.17). As for the influence of sex difference on the incidence of atrophic gastritis by Helicobacter pylori infection, the odds ratio among males was not significant (1.4, 95% confidence interval: 0.30-6.10), but the odds ratio among females was significantly high (9.8, 95% confidence interval: 2.82-34.11). These results suggest that Helicobacter pylori infection is associated with the incidence of atrophic gastritis. There may be a risk difference between males and females in the incidence of atrophic gastritis caused by Helicobacter pylori infection.