Adolescents and young adults (AYA) with acute lymphoblastic leukemia (ALL) constitute a distinct population from children and older adults. However, AYA represent a minority of patients enrolled onto either adult or pediatric clinical trials. As a result, little information is available regarding complete remission (CR), event-free survival (EFS) and overall survival (OS) rates for this age group, and the appropriate treatment regimen for this group of patients remains elusive. A systematic review of all published clinical trials, which provide data on treatment and outcome of AYA with ALL, has been summarized in an effort to determine whether they should be treated on pediatric or adult protocols. AYA with ALL have far superior outcomes when treated on more intensive pediatric regimens and are required specific collaborative trials in order to optimize and improved outcomes.(Korean J Med 73:459-463, 2007)