Circulating immune complexes (CIC) were measured in 133 biopsy-proven patients with various liver diseases. The correlation between CIC levels and other laboratory findings was investigated in each disease group, in order to assess if the increased C1q-binding activity found in these patients was related to particular features of the disease. CIC levels were not significantly different in HBsAg-positive and HBsAg-negative patients. No correlation was found between CIC levels and serum bilirubin, AST, ALT and C3 levels. A negative correlation with C4 levels and a positive correlation with immunoglobulin levels were found in the majority of the patients, while prothrombin time and albumin levels were negatively correlated to CIC levels only in patients with chronic active hepatitis. Increased CIC levels could represent a response to gut-associated antigens, a passive accumulation due to reduced hepatic function or both.