Marrow-ablative chemo-radiotherapy followed by hematopoietic stem cell rescue from an allogeneic source improves outcomes for children with high-risk acute leukemia. The first effective pre-transplant preparative regimens consisted of high-dose cyclophosphamide (CY) and total body irradiation (TBI). Subsequent attempts have been made to improve leukemia-free survival, by adding other chemotherapy agents to these agents. In previous clinical studies of total body irradiation, etoposide, cyclophosphamide (TBI-VP-16-Cy) in adult allogeneic bone marrow transplantation, there has been a high incidence of severe regimen-related toxicity. In this study, we investigated the safety and efficacy of this combination in 41 children who received TBI (12-14 Gy), VP-16 (30 mg/kg), and CY (60 mg/kg x 2) and then either matched sibling or alternative donor transplants for acute leukemia. There was only one case of fatal regimen-related toxicity. The estimated 3-year event-free survival for patients with early or intermediate stage disease was 68% (53-88%). The estimated event-free survival of patients with advanced disease was 17% (5-59%). TBI-VP16-CY is safe in pediatric transplantation, and it has good efficacy for transplant recipients with less advanced disease. Bone Marrow Transplantation (2000) 25, 489-494.