Health care workers (HCW), especially women (for example, pediatric nurses and day nursery workers), have been shown to be at risk for viral hepatitis A infections. In order to obtain a more precise estimate of the risk in Belgian HCW, a seroprevalence study was undertaken. The data from this study have been compared with the age-specific seroprevalence of anti-HAV in the general population (CP) as recently estimated. During 1996-1997, a sample of 5,068 employees in 22 general hospitals, geographically distributed over the Flemish and Brussels regions of Belgium, was tested for the presence of anti-HAV. Comparison of the anti-HAV prevalences in HCW and CP shows a significantly lower prevalence in HCW for the age groups 25-34, 35-44 and 45-54 years. Within these age-groups, employees performing catering tasks have the highest prevalence. This difference could be explained by socioeconomic parameters: overrepresentation of higher social classes in better educated HCW. The number of unprotected individuals in young and older age groups (25-54 years) is greater than in the general population. In view of the changing HAV epidemiology in western Europe, the number of unprotected persons will rise in the coming years. Considering the more severe course of the disease as age increases, vaccination may become important in the occupational health strategy for HCW.