The results of allogeneic stem cell transplantation for patients with chemotherapy-resistant non-remission acute leukemia have been very poor. We have used a melphalan-preceding intensified preparative regimen in which a six-day interval is set between melphalan 70 mg/m2 and the main part of the preparative regimen to avoid toxicity in 15 consecutive pediatric patients with refractory acute leukemia. Only one patient died of transplant-related toxicity within 100 days of transplant. One patient had refractory anemia originating from donor cells at three months after transplant. Eight patients relapsed at a median of six months after transplant; therefore, five of 15 patients have been in complete remission (CR) for a median of 61 months. Four of six patients who did not have blasts in their peripheral blood before melphalan are in CR This method seems to be safe and effective for refractory acute leukemia.