A baseline study on the vertical transmission of hepatitis B virus in Taiwan revealed that 15 percent of all pregnant women were persistent carriers of hepatitis B antigen and that 40 percent of their new babies developed a protracted antigenemia during the first 6 months of life. The incidence of acute hepatitis, cirrhosis, and hepatoma was high in Taiwan, and patients with these disorders had a fivefold to sixfold higher prevalence of hepatitis B antigen than healthy persons. Given the important public health problems of this disease in Taiwan and the rest of the Third World, this trial sought to answer the important question of whether hepatitis B immune globulin with a high level of antibody against the antigen would be of utility in combating the problem.