In order to prevent hepatitis B virus (HBV) infection of infants of hepatitis B surface antigen (HBsAg)-positive mothers, a nation-wide immunization programme was initiated in Italy in January 1984. During the first 3 years (1984-86), 651,667 out of 1726,000 pregnant women (37.8%) were screened for HBsAg; the percentage of mothers screened increased from 32% in 1984 to 51% in 1986 in 15 of the 21 Italian regions, where data by year were available. HBsAg was present in 15,640 mothers (2.4% of those screened); range by region 0.3-6.4%. All newborns of HBsAg-positive women, regardless of the mother's status of hepatitis Be antigen (HBeAg), were given a single dose (0.5 ml Kg-1) of a hepatitis B immune globulin within 24 h after birth and the first dose of plasma-derived hepatitis B vaccine within 7 days after birth. The immunization coverage rate was 80% in the 3-year period. Protective antibodies were found in greater than 97% of a sample of 1071 infants, immunized from different regions. No serious reactions were observed. On the basis of this field experience, it may be concluded that a nation-wide hepatitis B vaccination programme for infants of HBsAg-carrier mothers would be highly immunogenic and safe. Its implementation, however, requires continuous public education and cooperation from physicians.