Background: Helicobacter pylori infection and serum pepsinogen values are strongly related with stomach cancer. The aim of this study was to know what were these factors among general population. Methods: Subjects were randomly selected 633 control subjects in a nested case-control study for risk of stomach cancer. Most of them were from rural areas of Japan, Using frozen sera, pepsinogen I (PG I) and II (PG II) values and H. pylori antibody were measured. Those with PG I less than 50 ng/mL and the ratio of PG I to PG II (PG I/II) was less than 2.0 were defined as severe, those with PG I less than 70 ng/ml and PG I/II less than 3.0 were defined as mild and the other subjects were defined as no serological atrophy. Results: About 70% of the subjects were H. pylori seropositive and the seroprevalence did not depend on age or sex. Percentages of those with severe scrological atrophy increased with age from 10% in those aged 40-49 years to 38% in 70 and more, and percentages of those with mild serological atrophy were about 30% independent of age. Conclusions: The subjects, who were expected to represent populations of rural area of Japan, had high prevalence of both H. pylori infection and serological atrophy of gastric mucosa. These facts should be considered in discussing results of the nested case-control study. Copyright © 2005 by Japan Epidemiological Association.