Hepatitis B surface antigen (HBs-Ag) was detected histologically (by victoria blue-nuclear fast red staining) in the liver in 20-40% of liver cirrhosis and/or hepatocellular carcinoma (hepatoma) cases. In hepatoma cases, HBs-Ag was usually found in non-cancerous areas of the liver. However, some HBs-Ag positive cells were also found dispersed in cancerous areas; these were regarded as HBs-Ag-infected non-cancerous hepatic cells remaining undestroyed. There were a few cases where inconsistency was found between the results of the immunofluorescence technique using anti HBs-Ag serum and victoria blue staining in detecting HBs-Ag. This phenomenon was rare in non-cancerous areas, but was relatively frequent in cancerous areas.