The relationship between the presence of circulating immune complexes (CIC) and of HBsAg in the serum of patients with chronic liver diseases was studied in a group of 78 patients of whom: 16 with chronic persistent hepatitis (CPH), 39 with chronic active hepatitis (CAH) and 23 with liver cirrhosis (LC). The results showed a clear relationship between the incidence of CIC and the presence of HBsAg in the patients with persistent or active chronic hepatitis but not in those with liver cirrhosis. The presence of HBsAg was detected in the composition of CIC in only part of the cases (10/25 patients). This low incidence suggests that in chronic hepatitis other antigens can also participate in the formation of CIC.