Studies on the quantitative expression of the Major Histocompatibility Complex (MCH) in hepatocytes chronically infected by Hepatitis B Virus (HBV) report that an increased expression of these antigens could be related to a good immunological response. In the present work we analyze the expression of the MCH antigens in cryostatic sections of liver biopsies taken from subjects (19 children) with various forms of HBsAg positive chronic hepatitis. A high expression of HLA class I antigens and a high degree of hepatocyte necrosis was evident in Chronic Active Hepatitis (CAH) and Chronic Lobular Hepatitis (CLH). On the contrary, subjects with histological diagnosis of Chronic Persistent Hepatitis (CPH) showed a low expression of such antigens. There was however, the difference that in subjects with high hepatic cytolysis and high expression of HLA class I antigens, serum HBV-DNA was clearly present in almost all the cases with CAH, but not detectable in all cases with CLH. The expression of HLA class II antigens and of Beta2 microglobulin was the same in all 19 cases. All cases with HBV-DNA positivity with high class I antigen expression had active hepatitis which seems to suggest that all attempts at viral clearance on the part of the immune system have been in vain. We hope our paper will be an additional parameter for evaluating the course of hepatitis during Interferon treatment.