Recombinant hepatitis B vaccine has been shown to be as safe and effective as plasma-derived vaccines. However, its efficacy in the prevention of perinatal infection has not been fully evaluated in an endemic area. We recruited 110 high risk infants born to hepatitis B e antigen-positive-hepatitis B surface antigen (HBsAg) carrier mothers in a study of recombinant vaccine efficacy. They were randomized into 2 groups, A (54 infants) and B (56 infants), to receive 4 doses of vaccine, containing 20 or 10 micrograms of surface antigen, respectively, at 0, 1, 2 and 12 months of age. An additional 60 high risk infants were recruited later (Group C) and received three 20-micrograms doses of vaccine at 0, 1 and 6 months of age. All infants also received a dose (145 IU) of hepatitis B immunoglobulin soon after birth. Sera were collected at 0, 1, 2, 3, 6, 12 and 14 months of age to assay HBsAg and anti-HBs. At 12 months of age the HBsAg carrier rates were 7.4 and 1.8%, in Groups A and B, respectively. In Group C the HBsAg-positive rate was 3.3%. HBsAg was invariably first observed between 0 and 2 months of age. Virtually all noncarrier infants developed substantial titers of anti-HBs at 12 months of age. No serious adverse effect was observed after vaccination.