Chronic graft-versus-host disease (GVHD) of the liver usually presents as an indolent cholestatic disease in patients with skin, mouth, and eye involvement. We observed 14 patients in whom chronic GVHD of the liver presented with marked elevations of serum aminotransferases, clinically resembling acute viral hepatitis. Onset of liver dysfunction was at 294 days (range, 74-747 days) after allogeneic hematopoietic cell transplantation and coincided with a recent cessation or taper of immunosuppressive drugs. Median peak serum alanine transaminase (ALT) was 1,640 U/L (698-2,565 U/L), and median bilirubin was 12.3 mg/dL (0.9-55.9 mg/dL). All biopsies showed characteristic features of GVHD with damaged and degenerative small bile ducts. Other features included a marked lobular hepatitis, moderate to marked amounts of hepatocyte unrest, sinusoidal inflammation with perivenular necroinflammatory foci, and many acidophilic bodies scattered throughout the lobule. When high-dose immunosuppressive therapy was instituted soon after presentation, progressive improvement and eventual normalization of liver enzymes and bilirubin levels were observed. However, in cases in which the diagnosis was not made and therapy was delayed, a progressive cholestatic picture emerged with histologic evidence of loss of small bile ducts and portal fibrosis. We conclude that a distinct syndrome of chronic liver GVHD presenting as an acute hepatitis can be recognized in a patient at risk who is receiving no, or minimal, immunosuppressive medications. Liver biopsy is necessary to exclude viral causes of liver dysfunction and to confirm characteristic abnormalities of small bile ducts. Institution of high-dose immunosuppression can prevent progressive bile duct destruction and effect resolution of jaundice if given early.