In order to clarify the incidence of the delta agent among hepatocellular carcinomas (HCCs) in Kurume, where the hepatitis B infection and its related HCC are most prevalent in Japan, liver tissues from sero hepatitis B surface antigen-positive autopsy cases, with or without HCC, were immunohistochemically investigated for detection of the delta antigen. Only one patient (1.7%) among 58 patients with HCC was found to have delta-antigen in the nuclei in the hepatocytes, which were diffusely distributed throughout the non-cancerous liver. None of 26 patients with liver cirrhosis showed delta-antigen in the liver tissue. The incidence is so low that the delta agent is unlikely to have a role in the development of HCC in our areas.