The accepted histological categories of chronic hepatitis are chronic persistent hepatitis (CPH) and chronic active or aggressive hepatitis (CAH). A third form, chronic lobular hepatitis (CLH), encompasses those cases in which the lesion is predominantly within the lobules and in which portal and periportal inflammation are mild, CLH has many synonyms. International agreement on a reproducible and rational nomenclature of chronic hepatitis is still far from complete. CPH is characterized by portal inflammation. Histological definition is simple, but there are diagnostic pitfalls. The category may need subdivision on the basis of immunological studies. CAH should be regarded as a complex rather than a single disease, and it is important to specify the aetiology and pathological components in each instance. The concept of CAH must be altered to incorporate the lesion bridging hepatic necrosis (BHN). Piecemeal necrosis, accompanied by inflammatory infiltration, is considered to be the most important of the various pathogenetic factors in CAH, but BHN probably plays a significant part in accelerating the development of cirrhosis. An excessive portal and periportal inflammatory reaction with or without BHN, in a liver biopsy taken during the course of an acute hepatitis, helps to predict a possible chronic course.