In this study, patients will receive Mylotarg twelve days before the transplant. The first patients will receive Mylotarg at the lowest dose level. As the study continues, the dose levels will be increased as long as no severe side effects occur. Mylotarg may be given in the outpatient Ambulatory Treatment Center (ATC). Patients will be monitored in the ATC for eight hours on the day of infusion. For the next 5 days, patients will be evaluated in the Clinic on a daily basis or as per physician orders. One week before the transplant, all patients will be admitted to the hospital and will continue their treatment as inpatients. Patients experiencing side effects from their leukemia or leukemia treatment may need to be hospitalized earlier.