Data of occasional or periodic blood donors from 189 banks scattered throughout Italy were retrospectively surveyed for the period between 1974 and 1977. The prevalence of HBsAg positive subjects (PHA or RIA) among occasional donors during 1975-1977 was about 3% with no appreciable annual variation. The rate of HBsAg positivity in southern Italy (i.e. Campania, 4.32%) was higher than in northern Italy (i.e. Trentino, 0.30%). Only 0.27% of the occasional donors showed both HBsAg positivity and elevated serum transaminases levels. Among periodic donors the rate of infection, as indicated by the appearance of HBsAg in serum subsequent to the last donation, was approximately 0.5% per year. Only one-tenth of the periodic donors who acquired HBsAg also had hypertransaminasemia.