Thirty-four persistent healthy carriers of HBsAg (serum HBsAg detectable for longer than 3 months with normal liver function tests and normal liver histology or slight aspecific abnormalities) were discovered by routine testing of household relatives of B virus hepatitis patients. The carriers were followed-up for 11 to 37 months by clinical control, liver function tests and liver needle biopsy. None carrier had previous jaundice. During the follow-up period, in 17 of the 34 subjects, was there no evidence of deterioration in either clinical state, liver function of pathological findings. In 5 of the 34 carriers, HBsAg disappeared from serum after a period ranging from 6 to 12 months. The remaining 12 cases developed clinical and histological picture of acute viral hepatitis after 6 to 29 months (mean 12 months). Of these 12 patients, 6 recovered and become HBsAg; 2 remained HBsAg healthy carriers despite normalization of biochemical and histological abnormalities; 3 progressed from the acute stage to antigen positive CAH. The remaining one case could not be followed-up after the acute hepatitis. Our data indicate that the outcome of the HBsAg carrier state is unpredictable and stress the need of long-term follow-up surveillance.