An increasing number of volunteer unrelated donor bone marrow transplantations (VUD-BMT) are performed every year for hematological malignancies due to the availability of a large donor pool. Here we show the results of 36 VUD transplants from our institution using a chemotherapy-only conditioning regimen comprising busulfan 4 x 4 mg/kg and cyclophosphamide 2 x 60 mg/kg. All patients received heparin 200 IU/kg bw continuous i.v. infusion starting the day before conditioning until day +30. Thirty-four of 36 patients (94%) engrafted and no secondary graft failure was observed. The two non-engraftments occurred in patients with CML in blast crisis with extensive myelofibrosis. All 34 engrafted patients (100%) were in complete remission on day +30 as shown by bone marrow biopsy and cytogenetic examinations. No life-threatening treatment-related morbidity or mortality (TRM) were observed, in particular, no severe veno-occlusive disease (VOD) of the liver and no fatal pulmonary complication. Use of G-CSF significantly shortened the time of neutropenia by 5 days. GVHD prophylaxis consisted of CsA/methylprednisolone with or without MTX. Acute GVHD grade II-IV was observed in 18/34 patients (53%) and cGVHD in 12/27 patients (45%), who survived to day +100. In seven patients (four with HLA class I or II mismatch) anti-T-lymphocyte globulin (ATG) was added for acute GVHD prophylaxis. One of seven had aGVHD grade II and none developed grade III to IV GVHD or graft failure. We conclude that Bu/CY is a feasible, save and sufficiently immunosuppressive regimen for VUD transplantation. Severe acute GVHD might be avoided by additional use of ATG in GVHD prophylaxis.