hepatitis B surface antigen (HBsAg) to their newborn infants is an important cause for the development of hepatitis B infections and for the maintenance of the hepatitis B virus reservoir in the world (l-3). Immunization of infants born to HBsAg-positive women has been shown to almost completely prevent perinatal infection (4-6). In 1982, a study was initiated in three test areas in the Netherlands to detennine whether screening to identify HBsAg carriers among pregnant women could be successfully introduced in prenatal care and whether the newborns of these HBsAg carriers could be protected from perinatal infection of combined passive and active immunization. Hepatitis B vaccination, given concomitantly with the diphtheria-tetanus-pertussis-poliomyelitis (DTPpolio) vaccination, was compared to hepatitis B vaccination initiated immediately after birth as far as compliance, immunogenicity and protective efficacy are concerned. Initial results of the study, completed in December 1992, were described by Maze! (7 -8). On the basis of the preliminary results, a national program for the prevention of perinatal hepatitis B infection was launched earlier, in October 1989.