OBJECTIVE To explore the incidence and risk factors of hepatic events and overall survival among HBsAg positive leukemia patients after allo-hematopoietic stem cell transplantation (allo-HSCT). METHODS A retrospective clinical study was conducted at the bone marrow transplant unit in our hospital between March 2001 and November 2006. A total of 26 HBsAg positive leukemia patients were included in the study. 18 patients received HLA-identical sibling allo-HSCT, 7 patients received HLA-mismatched related and 1 patient received HLA-identical unrelated. All the patients were free from hepatitis C infection before and after allo-HSCT. HBV serologic markers, including HBsAg, HBeAg, HBsAb, HBeAb and HBcAb were tested. 2 patients were positive for HBV-DNA before allo-HSCT. RESULTS The cumulative incidence for acute graft vs host disease (aGVHD) grades I -IV was 50.0%. The cumulative incidence for chronic GVHD was 25.0%. 15 (57.7%) of all the patients had abnormalities of liver function after allo-HSCT. The types of hepatic disease were reactivation of HBV and hepatic GVHD. The cumulative incidence in 5 years for hepatitis B reactivation was 33.4%, the median day of hepatitis B reactivation was 82th (65th-159th) day. The virologic and clinical outcomes were compared between two groups; one received lamivudine as prophylactic (group 1) and the other did not receive lamivudine (group 2). After transplantation, 1 patient in group 1 and 7 patients in group 2 had hepatitis due to reactivation of HBV. The cumulative incidence for hepatitis B reactivation was statistically different between the two groups (P= 0.006). None in group 1 but 4 in group 2 died of HBV-related hepatic failure. 10 of the 26 patients died after transplantation. The overall survival (OS) in 5 years was 59.0%. The causes of death included hepatic failure (5 cases), lung infection (3 cases) and relapse of leukemia (2 cases). By multivariate Cox analysis, development of hepatic failure was a significant predictor of mortality (P = 0.000). CONCLUSION HBsAg positive leukemia patients often suffered from hepatic injury after allo-HSCT. The principal cause of hepatic damage was the reactivation of HBV. Hepatic failure caused by HBV was the principal reason of death. Prophylaxis with lamivudine in HBsAg positive leukemia recipients can reduce the reactivation of HBV.