In order to strengthen the anti-leukemia effect, we developed a new conditioning regimen with high dose busulfan, VP-16 and ACNU (BVA) for cytoreduction before stem cell transplantation. Fourteen patients with refractory acute leukemia received allogeneic bone marrow transplantation (BMT) or peripheral blood stem cell transplantation (PBSCT) after conditioning with the BVA regimen, 7; allogeneic BMT, 1; syngeneic BMT, 6; PBSCT. # Seven patients were transplanted in the first complete remission, and 8 patients were in their second or third remission. Although total body irradiation or cyclophosphamide was not included in this regimen, engraftment was obtained in all cases. Two patients suffered relapse, and one patient died of cytomegalovirus interstitial pneumonitis (IP) 64 days after PBSCT. The other 11 patients are alive and free of disease at a median follow up time of 647 days (98-1235 days). Major regimen-related toxicity was pulmonary complications such as IP (3 cases) and pulmonary edema (2 cases). However, all patients recovered rapidly following steroid therapy. The results indicate that this conditioning regimen is highly effective for the treatment of childhood acute leukemia.