BACKGROUND: Although increasing number of patients are survived after organ transplantation, morbidity and mortality due to cardiovascular disease is thought to be the key risk factor for the long-term tranplant survivors. Many studies have shown that posttransplant diabetes mellitus, dyslipidemia, and hypsrtension are major causes of accerelated atherosclerosis after organ transplantation. Immunosuppressants, rejection, family history of DM, certain HLA phenotypes, pretransplant age and fasting glucose concentration are suggested as etiopathogenic factors of posttransplant diabetes mellitus (PTDM) after solid organ transplantation, while the risk factors of PTDM after bone marrow transplantation (BMT) is unknown. The aim of our study to investigate the clinical characteristics and possible risk factors for PTDM after BMT. METHODS: Age, male to female ratio, body mass index, mean daily steroid dosage, mean daily cyclosporin dosage, incidence of graft versus host disease(GVHD), incidence of cytomegalovirus (CMV) disease, fasting plasma glucose concentra-tion, serum lipid profiles, and HLA phenotypes were retrospectively examined in 15 PTDM patients and 68 non-diabetic patients after allogeneic BMT. RESULTS: 1. Among 490 allogeneic BMT, PTDM developed in 15 patiants (3.1%). The mean duration from BMT to onset of PTDM was 26,6+/-33,9 days. 2. When compared between the PTDM and non-diabetic patients, mean daily steroid dosage, incidence of GVHD, and incidence of CMV disease were significantly different. 3, HLA phenotypes, HLA-DR52 and DR53, were more frequently observed only in PTDM patients. 4. At the onset of PTDM, we observed that fasting plasma glucose, total cholesterol, and LDL-cholesterol concentration were significantly elevated in pre-BMT state. CONCLUSION: We conclude that posttransplant diabetes mellitus after BMT, frequently develops in patients with a predisposition of high-dose steroid, GVHD, HLA-DR52 and DR53 phenotypes. This study suggested that high-dose steroid therapy, mainly due to GVHD, might be the critical factor in the onset of PTDM after allogeneic BMT and that the risk may be affected by HLA-DR52 and DR53 phenotypes.