Refractory acute leukemia (AL) occurs in a significant percentage of the AL patients and presents a therapeutic challenge. Allogeneic stem cell transplantation (allo-SCT) is the only curative option for these patients. Although many of the patients with refractory AL that undergo myeloablative SCT initially achieve complete remission, most relapse later on, and the long-term disease free survival is poor. In order to achieve better leukemic control, most transplant centers employ post transplant early withdrawal of the anti-GVHD immunosuppression; hence exposing the patients to high risk of GVHD associated morbidity and mortality. This study will try to address this common scenario, namely early and late relapse. The investigators will try to attain better leukemic control by re-inducing the patients, 6 weeks after the 1st transplant with further myeloablative treatment (busulfex and thiotepa) followed by allogeneic stem cell support (transplant II).