An unusual clinical presentation of chronic active hepatitis is the abrupt onset of symptoms and jaundice, suggesting acute viral hepatitis. In this report, six patients had the acute onset of a severe liver disease. Five of the patients were female and ranged in age from 13 to 64 years. Marked elevations in the total bilirubin (17.1 +/- 11.4 mg/dl), AST (1,346 +/- 352 mIU/ml), and ALT (1,043 +/- 213 mIU/ml) were present (mean +/- SD). Negative serologies for hepatitis A and B were found. Liver histology showed severe hepatocellular injury. A diagnosis of autoimmune chronic active hepatitis with acute features was made on the basis of high titers of antinuclear antibody and smooth muscle antibody and the presence of hypergammaglobulinemia. As immunosuppressive therapy is a beneficial treatment of autoimmune chronic active hepatitis, an acute presentation of this liver disease should be considered as an alternative diagnosis to acute non-A, non-B hepatitis in patients with these clinical characteristics.