In October 1989 routine screening for Hepatitis B surface antigen HBsAg) in all pregnant women was introduced in the Netherlands. In order to prevent hepatitis b infection in their offspring all infants of HBsAg-positive mothers receive passive active immunization. During the first 15 months of the programme about 70% of the estimated total number of pregnant women was screened for HBsAg in the regional laboratories appointed by the National Institute of Public Health and Environmental Protection. It is currently unknown whether the remaining 30% of the pregnant women were screened and if so, where. The overall prevalence of HBsAg-positivity was 0.45% in 1990, with a range of virtually 0% in rural areas to 0,9% in the city of Amsterdam. The overall percentage of HBsAg-positive women appeared to be much lower than the originally expected percentage of 0.8%. The question therefore is whether the women not reacted by the programme belong to the high risk groups for hepatitis B. Although a number of regional laboratories dit not provide details concerning their analytical performance, in general the laboratory methods used seemed to be adequate.