The results obtained at the end of the first three years of a hepatitis B vaccination campaign in Campania, are reported. HEVAC-B and H-B-VAX proved innocuous and efficacious in producing anti-HBs. Newborn babies and children produced anti-HBs more often and with higher titres than adults. Titre 10 mUI/ml of anti-HBs persisted, in the responders for at least 36 months on average. AVH by HBV was observed in two adult non responders. Transplacental or delivery infection was observed in 9.3% of the babies born of HBsAg positive mothers and more often among babies born of HBeAg positive mothers. Infection by HBV was observed in 6.0% of the babies, in 4.0% of the children and in 12.0% of the adults, in spite of the production of anti-HBs. HB-antigenemia, was as a rule transitory, but sometimes fluctuating or persistent. Careful observation during a prolonged follow up is necessary for these subjects.