To investigate the causes of impaired liver function (LF)* after BMT, 88 patients were included for analysis of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections, transplant methods, preconditioning regimens, and graft-versus-host disease (GVHD). Fifty of them (56.8%) developed abnormal LF after BMT and among them, 29 (32.9%) developed chronic hepatitis (CH). By univariate analysis, HCV infection, pretransplant abnormal LF, allogeneic BMT, and preconditioning regimen with total body irradiation were all significantly related to higher incidence of post-BMT impaired LF. However, only HCV infection, pretransplant abnormal LF, and acute GVHD were associated with higher incidence of CH. By multivariate logistic regression analysis, HCV infection and pretransplant abnormal LF were the two most significant interpreters for abnormal LF, especially for CH (odds ratios: 7.86 and 4.735, respectively) after BMT. Although the incidence of abnormal LF was found high in this study, there was no significant disadvantage in terms of survival for patients who developed abnormal acute and chronic liver function after BMT. However, a long-term follow-up is needed to evaluate survival pathology of CH, such as liver cirrhosis and hepatoma.