To assess the prevalence of antibodies to hepatitis A virus (anti-HAV) in future travellers, all visitors to the Zurich University Vaccination Center in July/August 1990 were invited to participate in a cross-sectional study. A total of 1126 future travellers were recruited to have a blood sample drawn and to complete a brief questionnaire. Among these, 35 refused or were excluded, thus 1091 were evaluated. The overall prevalence of anti-HAV was 16.5%. This rate was 5.9% in future travellers born in or after 1961, 11.8% in those born 1951-60, 21.4% in those born 1941-50 and exceeded 49% in all decades born in or before 1940. Risk factors for significantly elevated anti-HAV rates were place of birth or a stay exceeding one year in tropical, subtropical or Southern European countries and travel for occupational reasons. Compared with findings from earlier surveys conducted mainly among blood donors in Switzerland and elsewhere in Europe, the results of the present study show lower anti-HAV prevalence rates. In conclusion, it seems unnecessary to test future travellers for anti-HAV except if they are born before 1944, or have a history of jaundice or of prolonged stay in the tropics, subtropics or in Southern Europe.