AIMS: To clarify the relation between the serum titre of anti-Helicobacter pylori (H pylori) antibody and the extent of intestinal metaplasia of the gastric mucosa. METHODS: The serum anti-H pylori IgG titres of 95 asymptomatic individuals (mean age 65 years) undergoing an annual health examination were measured and compared with the extent of intestinal metaplasia (absent, moderate, or extensive), determined by examination of multiple endoscopic mucosal biopsy specimens. Serum pepsinogen I (PGI) levels, as a marker for gastric atrophy, were also measured. RESULTS: The prevalence of seropositivity for H pylori antibody was high (> 80%), regardless of the extent of metaplasia. However, there was a negative association between the extent of metaplasia and the anti-H pylori titre: 75% of the subjects in the group without metaplasia had high (3+) antibody levels, as did 43% with moderate, and 37% with extensive metaplasia (absent v extensive). The inverse relation between the titre and the extent of metaplasia was evident when examined in those with normal PGI (> 30 ng/ml), whereas no such relation was apparent in subjects with low PGI (< or = 30 ng/ml). CONCLUSIONS: The anti-H pylori titre correlates inversely with the extent of intestinal metaplasia, particularly in subjects with less marked gastric atrophy.