Ever since the emergence of the concept of catharral jaundice by Virchow, viral hepatitis has eluded scientists as a pathogenetic enigma. A tremendous new impetus was given to hepatitis research by Baruch Blumberg's discovery of his 'Australia Antigen', now known as hepatitis B surface antigen. This led to an unheard-of outburst of research activity to elucidate the nature of the virus, its chemical and antigenic composition, its epidemiology, and pathogenetic mechanisms in the causation of liver disease. Coinciding with this period, modern medical science witnessed impressive progress in the analysis of the extraordinarily complex mechanism of immunological reactions. Immunohistochemical techniques for the detection of hepatitis B viral components are a product of this scientific progress in both areas. The application of such tech­ niques forms the core of this work. It represents a vast amount of work, performed during the course of several years, with meticulous application of advanced immunohisto­ chemical techniques, combined with histopathology and clinical-patho­ logical methods. This has resulted in the compilation of original results and new insights into the cellular and tissular localization of the anti­ genic components of the hepatitis B virus in different forms of chronic liver disease. The most outstanding results are the demonstration of the superior sensitivity of the applied immunohistochemical technique in the search for viral components in chronic hepatitis patients. and the differ­ ential distribution patterns of hepatitis B surface antigen in the various forms of chronic liver disease.