Intensive chemotherapy regimens for children with acute lymphoblastic leukemia (ALL) have greatly improved, and the majority of children with precursor B-cell ALL are able to achieve a complete remission (CR), with an induction rate approaching 98% and a 5-year estimated event-free survival rate (EFS) of approximately 80%. Although there have been dramatic improvements over the last several decades in both the EFS and overall survival (OS) rates in young children with ALL, the results in adult clinical trials have not kept pace. Current adult treatment regimens result in CR rates in the 80% range, with EFS at 5 years of only 30%-40%. Adolescents and young adults represent a minority of patients enrolled onto either adult or pediatric clinical trials. As a result, little information is available regarding CR, EFS, and OS rates for this age group, and the appropriate treatment regimen for this group of patients remains elusive. Recent studies suggest that young adult patients have far superior outcomes when treated on more intensive pediatric regimens. In addition, new insights into the molecular pathogenesis of T cell ALL have led to new therapeutic strategies.