An enzyme-linked immunosorbent assay has been used to diagnose serologically the prevalence of Helicobacter pylori infection in Asian life-long vegans. There was no difference in the seropositivity between these individuals and a group of age-and sex-matched Asian meat-eaters, indicating the meat consumption is not a risk factor for H. pylori infection. However, both Asian groups had a higher prevalence of infection than age- and sex-matched Caucasian meat-eaters. Additionally, the Asian individuals had a wider range of specific IgG antibody concentrations than the Caucasians. This did not appear to be due to antigenic cross-reactivity between H. pylori and Campylobacter jejuni. The significance of these observations to the establishment of cut-off levels for the serodiagnosis of certain ethnic groups is discussed.