We describe a patient with bcr/abl-positive acute mixed lineage leukemia who successfully underwent transplantation in primary induction failure, using unmanipulated bone marrow from a human leukocyte antigen (HLA)-haploidentical cousin. The tumor burden was successfully reduced by the administration of imatinib mesylate (STI571) before transplantation. As graft-versus-host disease (GVHD) prophylaxis, a combination of tacrolimus and a short course of methotrexate, methylprednisolone, and mycophenolate mofetil was used. Hematopoietic reconstitution was rapid, and acute GVHD was limited to the skin (grade I). The patient is still in complete remission past day +400. This successful case suggests that HLA-haploidentical transplantation using unmanipulated marrow from a distantly related relative can be considered for patients in urgent situations who do not have HLA-identical donors.