Fifty patients with acute myeloid leukemia (AML) or chronic myeloid leukemia (CML) underwent allogeneic bone marrow transplantation between October 1988 and January 1997. Patients received 8 mg/kg of busulfan (BU) with 120 mg/kg of cyclophosphamide (CY) followed by 10 Gy of total body irradiation (TBI). Twenty consecutive patients with AML in first remission (n = 9) or CML, in chronic phase (n = 11) entered the study (group I). Thirty consecutive patients with advanced myeloid malignancies including AML (n = 19) and CML (n = 11) also entered the study (group II). The probability of leukemia-free survival at 5 years was 85% for group I patients and 50% for group II patients. Severe regimen-related toxicities occurred in 16% of patients (two in group I, six in group II). The most common sites affected by severe toxicities were lung (n = 6), liver (n = 2) and heart (n = 2). The relapse rate was higher for patients allografted in advanced stages of disease (O% at 5 years for group I and 28% for group II). These results suggest that BU + CY + TBI is a very effective conditioning regimen in patients with myeloid malignancies.