We have studied five long-term survivors of allogeneic bone marrow transplantation. All exhibited prolonged serum biochemical evidence of hepatic dysfunction during 2− to S-year periods of follow-up. Two patients developed chronic cholestasis without pruritus. The serum of a third patient became chronically positive for HBsAg. A fourth patient developed an acute hepatitic syndrome and high titers of antibody to cytomegalovirus. Nuclear, mitochondrial, and smooth muscle antibodies were not detected. Seven liver biopsies, obtained from three of the patients, all revealed a hepatocellular necroinflammatory lesion suggestive of chronic active hepatitis, a paucity of interlobular bile ducts, and intrahepatic cholestasis. Possible etiologies for these hepatic changes include reactivation of chronic non-A, non-B hepatitis and chronic graft-versus-host disease perse. Our study emphasizes the diagnostic problems posed by hepatic dysfunction occurring in an immunosuppressed multiply-transfused patient after bone marrow transplantation.