Serum immunoglobulins and C3 levels, auto-antibodies to smooth muscle (SMA), mitochondria (MA), and nuclei (ANA), rheumatoid factors (RF), HB-antigen and HB-antibody were studied in 9 groups of liver disease. Hypergammaglobulinaemia was a prominent feature in most groups, IgG being particularly raised in active chronic hepatitis, IgM in primary biliary cirrhosis, and IgA in alcoholic liver disease, respectively. IgE was often increased in alcoholic liver disease and was frequently low in hepatic tumours, whereas IgD showed no typical pattern in any liver disorder. SMA was most frequently found in active chronic hepatitis (68%), and MA in primary biliary cirrhosis (58%), while ANA was detected in 50% of the patients with active chronic hepatitis. However, a pronounced over-lap of tissue antibodies was observed among the various groups of liver disease, particularly in active chronic hepatitis and primary biliary cirrhosis. The concurrent presence of SMA and ANA was most frequent in active chronic hepatitis. It was not excluded that antibody titres might have provided better diagnostic discrimination, since titration of antibodies was not performed. Low C3 levels in active chronic hepatitis were correlated with low levels of other liver-synthetized proteins, and no evidence was found of increased consumption by immunologic reactions.