Among 466 hospitalized patients with serologically verified acute hepatitis B, 440 individuals (94.4%) could be followed up until normalization of liver function had occured, or for at least one year. In 90.2% of the patients followed-up liver function including galactose tolerance) returned to normal within four months after onset of illness. Chronic persistent hepatitis B surface antigen (HB Ag) for at least one year in 14 patients (50%). Liver biopsy was performed in consistent with CPH in all cases. Histological signs of chronic aggressive hepatitis developed in 15 patients (3.4%) and persistence of HB Ag was observed in 11 of these patients (73%). No histological follow-up was performed in patients with normal liver function within four months after onset of illness. Cprticosteroid treatment in 56 patients with prolonged symptoms did not seem to predispose to persistence of HbsaG in the serum.