ABSTRACT—A morphologic study with immunohistochemical detection of the viral antigens of hepatitis B and Delta was performed on 36 liver specimens from patients with delta positive chronic viral hepatitis B. Electron microscopy was performed in 9 cases. No light microscopic or ultrastructural features specific for hepatitis D were observed. Lymphocytic infiltration occurred more often close to hepatocytes containing either hepatitis Delta antigen or hepatitis B core antigen in the cytoplasm, suggesting an involvement of cellular immune mechanisms in chronic hepatitis D as well as in hepatitis B. The simultaneous expression of both HBcAg and Delta antigen in occasional specimens over longer time periods indicates the possible co‐existence of both viruses without mutual inhibit