Autologous bone marrow transplantation (ABMT) is a therapeutic approach that permits the administration of high-dose chemoradiotherapy followed by the infusion of the patient's own marrow, previously collected during remission and cryopreserved. In recent years, ABMT has been increasingly used as a treatment for acute leukemias. The mechanisms underlying leukemic relapse represent the most exciting and controversial aspects of ABMT. At least three factors may be responsible for leukemic relapse in patients receiving ABMT: (a) minimal residual disease; (b) leukemic cells reinfused with the graft; and (c) the lack of a graft-versus-leukemia effect. Techniques for pharmacological marrow decontamination, clinical results obtained with ABMT, and new perspectives opened by growth factors and cytokines are reviewed.