A low level of serum pepsinogen I (Pg I) is a risk factor for gastric cancer (GC); low levels of Pg I and the pepsinogen ratio (Pg I:Pg II) are correlated with chronic atrophic gastritis. We report serum Pg levels and compare the degree of association with GC among Japanese and non-Japanese Brazilians. Sera were cross-sectionally ascertained from 93 Japanese Brazilian patients category matched by age and sex with 110 controls, and 228 non-Japanese Brazilian patients individually matched by age and sex with one control. Among non-Japanese Brazilians, GC was associated with a Pg I level <30 ng/ml (odds ratio [OR], 2.5; 95% confidence interval [CI], 1.7-3.8) and a Pg I:Pg II ratio < 3.0 (OR, 3.4; 95% CI, 2.2-5.3). However, among Japanese Brazilians, the association was present with a level of Pg I < 30 ng/ml (OR, 3.5; 95% CI, 1.9-6.3), and was weak with a Pg I:Pg II ratio < 3.0 (OR, 1.3; 95% CI, 0.73-2.4). Serum Pg I may be preferred to the Pg I:Pg II ratio to study the association between Pg and GC among Japanese Brazilians.