Epidemiological data about the prevalence of Helicobacter pylori positivity are presented in a large population of symptom-free paediatric and adult patients in Belgium (n: 1180, age range: 1 to 40 years). The investigated patients belonged to different ethnic backgrounds and are representative for the general population of Brussels. The overall prevalence of Helicobacter pylori positivity was 18.0%. We observed a significant increase in the number of positive patients with advancing age, ranging from 6.4% in the youngest age group (1 to 5 years) to 36.4% in the age group from 36 to 40. Furthermore, a significantly higher prevalence was observed in non-Caucasian patients when compared to caucasian subjects, even if both groups were born in Belgium and have been living in the same area ever since (p < 0.001). We conclude that the overall prevalence of Helicobacter pylori positivity in asymptomatic subjects in Belgium should not be underestimated. Their number increases with age and there are significant ethnic differences. The meaning of these "asymptomatic carriers" still needs to be elucidated, but their prevalence should be considered in future studies about the role of Helicobacter pylori in upper gastro-intestinal pathology.