Twenty-two patients with previous hepatic compromise who underwent allogeneic bone marrow transplant (BMT) for treatment of hematologic malignancy or other hematologic disease between 1984 and 1990 were chosen for the present study. After transplant, 19 (86.4%) of the patients developed hepatitis, including six cases (27.3%) of acute hepatitis, 12 (54.6%) of chronic hepatitis and one uncharacterized hepatitis. Nine chronic hepatitis patients were followed-up for 7-56.5 months (medium 35.5 months) with biochemistry studies and ultrasonography. Throughout the observation period, liver cirrhosis or hepatoma were not detected and no patients developed veno-occlusive disease. Furthermore patients who developed hepatitis after transplant had worse prognoses. Based on serial serological survey of the various hepatitis B virus (HBV) antigens and antibodies, we have found that most of the recurrent viral hepatitis in transplant patients could be attributed to the reactivation of the virus. In addition, the use of immunosuppressive drugs, persisting infection by HCV and the development of graft-versus-host disease may also play a role in modulating the course of viral hepatitis in BMT patients.