In the first decade of the new millennium, multiple studies have begun to change our thinking about the treatment of adults with acute lymphoblastic leukemia (ALL). In pediatric patients cure rates in the range of 80% to 90% are now attainable. While adult patients with ALL now have a 90% complete remission (CR) with modern chemotherapy, most patients will relapse, and leukemia-free survival with 3 to 7 years of follow-up in large series is only in the range of 30% to 40%. The poor outcome of chemotherapy in adults with ALL as compared to children relates to multiple factors, including poor tolerance of intensive courses of chemotherapy and a higher incidence of poor prognostic subtypes of ALL such as Philadelphia chromosome-positive ALL and a lower incidence of favorable subtypes such as the t (12; 21).