Bone marrow transplantation (BMT) is increasingly being recommended for relapsed acute lymphoblastic leukemia (ALL). A number of transplant options exist, although the best results have used HLA-matched sibling donors. Allogeneic BMT using closely matched unrelated donors and partially matched or haploidentical family member donors have become more popular with improvements in control of graft rejection and graft-versus-host disease. Autologous transplantation is also an option for relapsed ALL although these types of transplants continue to be associated with higher secondary relapse rates. Despite many advances in the transplant field, the best myeloablative preparative regimen for BMT is still unknown. The toxicity of these regimens continues to contribute to significant post-transplant morbidity, prompting consideration of standard chemotherapy for a select group of patients with relapsed ALL. Better recognition and treatment of many post-transplant complications have led to improved overall survival in BMT patients over the past 10 years. This article will review the different types of transplants performed in children with relapsed ALL and detail some of the present controversies in this area.