In order to assess the present hepatitis B immunization program in Stockholm, Sweden, 212 children of HBsAg carrier mothers were followed up 2-9 years after birth. In babies of HBeAg-positive mothers a combined passive and active immunization schedule with hepatitis B immunoglobulin (HBIG) and hepatitis B vaccine was used. Among 25 children to such mothers, 1 HBsAg carrier and 5 children with asymptomatic seroconversion were found. To newborns of HBeAg-negative/anti-HBe-negative mothers, only vaccine was given. Among 15 such children, no HBsAg carrier (but 1 child with an asymptomatic seroconversion) was found. In babies of HBeAg-negative/anti-HBe-positive mothers, immunization was withheld between 1983 and 1987. Among 90 such children, 1 HBsAg carrier and 8 asymptomatic seroconversions were detected. After 1987, newborns in this group were vaccinated whereafter 3 asymptomatic seroconversions were found among 82 children. We conclude that in low prevalence areas a screening program for HBsAg should be offered to pregnant women originating from hepatitis B endemic regions, since immunoprophylaxis gave long-term protection to most children at risk. Children born to HBeAg-positive mothers should receive vaccine in combination with HBIg, whereas for children of mothers lacking HBeAg, vaccination only seems sufficient, at least if a rapid vaccination schedule is used.