Hepatitis B reactivation following chemotherapy withdrawal may result in hepatitis, hepatic failure and death. We studied the clinical outcome and the causes of hepatic events of hepatitis B surface antigen positive recipients undergoing bone marrow transplantation. Twenty-four hepatitis B surface antigen patients were matched with 24 hepatitis B surface antigen negative patients for age, sex, CMV positive serology, underlying hematological disease and type of bone marrow transplantation. Post-BMT, there were 18 patients in the hepatitis B surface antigen positive group and four patients in the hepatitis B surface antigen negative group who suffered from hepatitis (P < 0.05). Thirteen of the 18 hepatitis were related to HBV reactivation in the hepatitis B surface antigen positive group and none of the four hepatitis in the hepatitis B surface antigen negative group (P = 0.01). The hepatitis B surface antigen positive group also had an increased incidence of acute graft-versus-host disease of liver (6 vs 1, P = 0.03). However, there was no significant increase in the incidence of veno-occlusive disease (10 vs 7, P = 0.40) and persistent hepatitis (3 vs 0, P = 0.07) in the hepatitis B surface antigen positive group. Using the log-rank test, there was no significant difference in survival between the hepatitis B surface antigen positive and negative recipients.