The constant and inconstant light microscopic changes in liver biopsies from patients with acute viral hepatitis are reviewed. The constant changes are essential for the diagnosis, and the distribution of ceroid (and often of haemosiderin) is important in the staging of the disease. Many and large piecemeal necroses in the acute stage are often followed by chronic aggressive hepatitis. A key to the understanding of the development of regeneration nodules - and thereby to posthepatitic cirrhosis - is portal-central bridging with subsequent formation of septa. Bridging and formation of septa is almost always preceded by piecemeal necroses in the acute stage and also by confluent necroses in 1/3 - 1/2 of the cases.