The incidence of hepatitis B virus (HBV) and hepatitis D virus (HDV) infection is in rapid decline in Southern Europe, due to the improvement in hygiene and economic conditions and the vaccination campaigns against hepatitis B. These changes have led to a shift from the classic form of chronic hepatitis B due to the wild-type virus, expressing hepatitis B e antigen (HBeAg) to a liver disease due to a mutated virus which does not express the HBeAg (e-minus mutant). Very interestingly, HBV-DNA has been detected in the liver tissue and in the serum of some subjects who lack hepatitis B surface antigen (HBsAg) in serum. This" occult" infection may be responsible for the residual cases of acute hepatitis B and might influence the course of chronic liver diseases of different aetiologies. A further consequence of the control of HBV infection is a spectacular decline in HDV circulation. At present only 8% of the HBsAg carriers in Italy have anti-HDV antibodies, vs 23% in 1987. Most of the patients with HDV infection are over 40 and present a mild liver disease or a slowly progressive cirrhosis. These epidemiological data support the concept that the epidemiological changes influence the clinical pattern of chronic hepatitis.