Bone marrow transplantation (BMT) from an HLA-matched sibling donor can cure 15% of end-stage patients with refractory acute leukemia. Failures are largely due to acute or chronic graft-versus-host disease, idiopathic or cytomegalovirus-associated interstitial pneumonitis, veno-occlusive disease of the liver, opportunistic infections, and leukemia relapse. The post-BMT leukemia relapse rate has been reduced from 65% to 20-40% by performing BMT in first complete remission (CR). Overall, about 50% of such patients become long-term tumor-free survivors. Younger patients do far better than older ones. A prospective comparative trial for acute nonlymphoblastic leukemia (ANL) in first CR revealed that BMT was more likely than chemotherapy to be fatal within the first 6 months after induction but that the probability of long-term tumor-free survival thereafter was significantly greater after BMT than after chemotherapy. It is recommended that patients less than 30 years old with ANL should undergo BMT while in first CR, whereas those patients over 30 years old should postpone BMT to the earliest sign of relapse.