Acute leukemia is the most common childhood malignancy, representing 30% of all cancer in American children under the age of 15 years and 12% of cancer cases in those ages 15 to 19 years old. In the United States, approximately 2500 new cases are diagnosed annually; 80% of these are acute lymphoblastic leukemia, 15% are acute myelogenous leukemia, and 5% belong to the chronic leukemia category.(1) The survival rates of children with acute leukemia have increased dramatically in the last 40 years.(2-5) The most success in outcome has occurred in acute lymphoblastic leukemia, although improvement is also being reported in acute myelogenous leukemia in the past few years. Progress comes from treatment strategy modifications on the basis of observations made in sequential large-scale therapeutic trials, an approach that serves as a paradigm for research in other malignant diseases.