In nine patients with advanced acute or chronic leukemia, we performed allogeneic hematopoietic stem cell transplantation (HSCT) following a modified myeloablative conditioning regimen intended to optimize the intensity of conditioning. This regimen consisted of intravenous busulfan 8mg/kg, cyclophosphamide 120mg/kg and total lymphoid irradiation 7.5 Gy. The median age of the patients was 30 years (range 18-59). Stem cell sources were related bone marrow in two, related peripheral blood in one, and unrelated bone marrow in six patients. Prophylaxis against acute graft-versus-host disease (GVHD) was cyclosporine and short-term methotrexate. Acute GVHD appeared in six patients (67%), grade II in all. Extensive chronic GVHD occurred in three of seven evaluable patients. The median follow-up period after HSCT was 813 days (248- 1,702). Of nine patients, five relapsed or progressed after HSCT. However, no patient relapsed or progressed within 100 days after HSCT. During the full follow-up period, transplant-related mortality (TRM) was not observed. The two-year overall survival and event-free survival were 88.9% and 50.0%, respectively. Our results suggested that we might reduce the incidence of TRM and simultaneously control disease by using an optimized conditioning regimen for HSCT.