Among infants born to women in whom sera are positive for both the hepatitis B surface antigen and the e antigen, 85% to 90% are infected with hepatitis B virus and become chronic hepatitis B surface antigen carriers. In a study to assess the effectiveness of passive-active prophylaxis (hepatitis B immune globulin and hepatitis B vaccine) of such infants, we screened 18,842 pregnant Asian-American women: 8.7% were positive for hepatitis B surface antigen and 3.0% were also positive for hepatitis B e antigen. Thus far, 113 infants have received hepatitis B immune globulin (0.5 mL at birth) and hepatitis B vaccine (three 20-micrograms doses beginning at birth or at 1 month) and have been followed up for nine to 18 months. Among these infants, 16 have become chronic carriers, an incidence of only 14.2%. All of the uninfected infants have retained high levels of antibody to surface antigen, suggesting that they have had an active immune response to the vaccine and should have long-term protection against hepatitis B virus.