Tissue samples from 180 unselected necropsy cases of various forms of hepatitis were examined by histopathology and immunofluorescence. The hepatitis forms studied included acute fulminant hepatitis (28 patients), subacute hepatitis (48 patients), acute fatal hepatitis (24 patients), chronic aggressive hepatitis (26 patients), liver cirrhosis (49 patients), and “minimal” hepatitis (5 patients). Hepatitis B surface antigen and hepatitis B core antigen were detected in 101 patients (56.1 per cent). In these, lesion-bound immune complexes of, hepatitis B surface antigen were found in the liver and extrahepatic locations in 77 patients (76.2 per cent). The latter included activated germinal centers of lymph nodes and spleen, focal hyaline lesions of splenic and renal arterioles, necrotic and/or proliferative lesions of small and medium-sized arteries, and kidney glomeruli with mild proliferative and degenerative lesions. There was an inverse relation of the approximate amounts of hepatitis B surface antigen in the liver and the liver damage, the latter being directly proportional to the amount of HBS Ag immune complexes in the liver and indirectly proportional to their amount in extrahepatic locations and to the severity of lesions at these sites.