A randomized double-blind, placebo-controlled efficacy trial of hepatitis B immune globulin (HBIG) for prevention of the mother-to-infant transmitted HBsAg carrier state was conducted in Taiwan where the carrier rate in the general population is 15 to 20%. HBIG was given immediately after birth to infants of e antigen positive HBsAg carrier mothers, and all infants were followed for at least 15 months. Among 61 placebo recipients, the carrier rate was 92%; compared with 26% among 57 infants who received 0.5 ml HBIG at birth, 3 months, and 6 months, and 54% among 67 infants who received a single 1.0 ml dose of HBIG at birth only. Efficacy was 71 and 42%, respectively, for the two treatment schedules. The most common response of HBIG-treated infants was passive-active immunization which was 27% in the single-dose group and 61% in the three-dose group. Some of the infants who became carriers were probably infected as HBIG protection waned, and we expect that higher efficacy can be achieved by hepatitis B vaccine in conjunction with HBIG.