Abstract
An electron microscope study was made of liver biopsy material obtained during life or shortly after death from 11 patients. In three of them, where serum was positive for Australia antigen (two had serum hepatitis and one active chronic hepatitis) the hepatocytes contained characteristic particles within membrane-bound cytoplasmic vesicles. The appearance of these particles was very similar to that of the Australia antigen particles found in the serum. Two sizes of cytoplasmic particles were observed, with average diameters of about 26 and 46 nm. Particles of both sizes often had a membrane-like outer component and a moderately electron-dense inner component. They differed in both size and structure from the mainly intranuclear particles described by previous authors and which were not found in the present patients. The nature of the vesicles containing the particles was not apparent.