Allogeneic marrow transplantation has emerged as a curative therapy for many patients with acute leukemia. The ability to cure patients of their disease is dependent on the remission status of the patient. For patients with acute myelogenous leukemia, up to 60% of patients can become long-term, disease-free survivors, whereas a similar number of patients with high-risk acute lymphoblastic leukemia can also achieve cure of their disease. The improved results with marrow transplantation have allowed the application of this therapy for patients up to the age of 50 years. Even patients with therapy-related leukemias can benefit from this approach. Although relapse is still a problem in all remission stages, current studies suggest that improved preparatory regimens, in combination with better treatment of graft-versus-host disease and prevention of cytomegalovirus pneumonia, will continue to improve the overall results of this therapy for patients with acute leukemia.