The clinical, biochemical and histological characteristics of 13 cases of acute hepatitis A were evaluated. In 10 biopsies moderate to severe cholestasis was seen consisting of bile thrombi, cholestatic liver cell rosettes and ductular transformation of hepatocytes as shown on keratin- and S-100 immunostaining. The periportal spotty necrosis may play a role in the pathogenesis of cholestasis in hepatitis A by creating an interruption in continuity of bile flow. In 6 cases, abnormal ductular epithelium was seen resembling the ductular lesion in septicemia. Such ductular lesion may be related to the accumulation of leucotrienes as a result of cholestasis.