Epidemiologic data about the prevalence of Helicobacter pylori positivity as determined by serology are presented in a large series of asymptomatic subjects (n = 1046). Serology is nowadays generally accepted as a valid non-invasive screening method for the detection of a Helicobacter pylori infection. Blood samples were taken from apparently healthy children (n = 480; aged 1-17 years) and pregnant women (n = 566; age 18-40 years) who were admitted for routine pre-surgery or pre-natal blood analysis. 162 (15.5%) had a positive titer for Helicobacter pylori. There was a significant increase in the number of positive patients with increasing age (ranging from 6.2% in the age group of the 1-5 years old to 31.0% in the age group of the 36-40 years old (p < 0.01). The meaning of this relatively high prevalence of "asymptomatic carriers" remains to be evaluated. A long-term follow-up of these patients should be considered to evaluate if they will develop clinical manifestations suggestive for Helicobacter pylori infection.