There are three different treatment groups in which leukemia and lymphoblastic lymphoma can be divided and they differ slightly in the types and amounts of chemotherapy drugs used during the 2-years of therapy. Participants are assigned to the different categories based on the features of their leukemia or lymphoma, such as their age, white blood cell count, and results of other tests. The three different treatment groups are called "Standard Risk", "High Risk" and "Very High Risk".