Relapse of leukemia following successful remission-induction therapy remains a major obstacle in the treatment of patients with acute leukemia. Leukemia recurs most frequently in patients with acute myeloblastic leukemia (AML) and high risk acute lymphoblastic leukemia (ALL) following chemotherapy and less often in patients with low risk ALL and particularly in patient groups> submitted to allogeneic marrow transplantation. ' It is likely that the great majority of these recurrences originate from residual leukemic cells that survive initial remission-induction chemotherapy. Today, several...