Passive and active immunization for the prevention of hepatitis B virus (HBV) transmission in neonates born to HBeAg positive carrier mothers was studied using different kinds and dosages of combined hepatitis B immunoglobulin (HBIG) and hepatitis B vaccine. The long term efficacy of these various immunoprophylaxis programmes was evaluated up to 3 years of age. Eight groups of neonates, 20 in each group, received HBIG either the usual dose of 100 IU intramuscularly or intravenously or increased dose to 200 IU, combined with different kinds of hepatitis B vaccine either in full dose or half dose given in different schedules of 0, 1, 2 or 0, 1, 6 months, in some groups also received a booster dose at 12 months. After follow-up for 3 years, there were no statistical significant differences of the results between these 8 different immunoprophylaxis programmes, either in the rate of seroconversion or the protective efficacy as well as the antibody response (anti-HBs titer). The seroconversion rates after 3 years of age in all 8 groups were in the range of 63.6 to 92.9 per cent. The protective efficacy rates at 3 years of age were in the range of 69.7 to 100 per cent.(ABSTRACT TRUNCATED AT 250 WORDS)