Helicobacter pylori is rarely found in gastric biopsy specimens from individuals with atrophic gastritis of the body mucosa. To determine if subjects with atrophic body gastritis have evidence of previous infection with H. pylori, immunoglobulin G antibody to H. pylori was measured by enzyme-linked immunosorbent assay in sera of 399 Finnish subjects. In 124 subjects, multiple biopsy specimens from body and antrum had been evaluated for the presence of H. pylori by Giemsa staining. Antibody correlated well with H. pylori staining except in the subgroup with atrophic body gastritis, in whom the prevalence of seropositivity (86%) was significantly greater than the prevalence of positive staining (33%) (P less than 0.001). Twenty-five subjects had positive antibody and negative staining. This group had a significantly higher prevalence of atrophic body gastritis (80%), lower maximal acid output, lower serum pepsinogen I levels, and higher serum gastrin concentrations than did seropositive subjects with H. pylori. These data suggest that most patients with atrophic body gastritis, despite having a low incidence of current overt infection, have been infected with H. pylori at some point in their lives.