Two hundred and five babies were accepted into the study, which was actually conducted on Taiwan through a contract to the Community Blood Council of Greater New York. Only those babies born of mothers who had HBsAg complement fixation titers of 1:8 or greater were included in these studies. At birth, blood was obtained from the mothers and cord blood from the infants. Follow-up bloods were obtained from both the mother and baby when the infants were 1, 3, 6, 12, 24 and 36 months of age. In addition, all household family contacts were bled at least once during this period.