Authors have investigated the hepatitis B and D virus antigens in the liver tissue of 30 HBsAg and/or anti-HD seropositive patients (23 males, 7 females, age: 20-65, mean: 44 years) by immunohistochemical method. The immunohistochemical identification of HBsAg, HBcAg and HDAg in 42 liver sample (36 obtained by percutaneous biopsy, 6 from dissection) of 30 patients was performed with Dako and Sorin Biomedica kits. The detailed virus serologic examinations were carried out with Biomedica and Abbott kits by radioimmunoassay and ELISA methods. Examining 36 liver tissue samples of 27 HBsAg seropositive patients, HBsAg could be demonstrated in 31 cases. Each patient suffering of active HBV and/or HDV replication was HBsAg positive by immunohistochemistry, while the tissue samples of patients in integrational phase of HBV infection were positive in only 9 cases of 14. There was no HBsAg tissue positivity in HBsAg seronegative cases. 7 of 16 tissue samples of 12 patients classified to active HBV replication state were HBcAg positive by immunohistochemistry. HBcAg could be detected in the liver tissue of each HBe seropositive patient, while in only 3 of 8 cases with only IgM anti-HBc seropositivity (indicating low level of HBV replication). Tissue HBcAg positivity, indicating active virus replication, was verified in 2 of 11 patients classified to HBV integration state by serology. Authors detected HDAg tissue positivity only in cases with serologically active HDV replication (IgM anti-HD seropositive) and HDAg could also be identified from liver tissue in each IgM anti-HD seropositive case. No HBsAg, HBcAg and HDAg tissue positivity was observed in HBsAg negative cases. Authors emphasise mainly the importance of immunohistochemical detection of HBcAg and HDAg completing the serologic diagnosis of chronic HBV and HDV infections, helping the verification or exclusion of active virus replication being essential for selecting adequate therapy.