There has been tremendous progress in the treatment of acute lymphoblastic leukemia (ALL) with modern chemotherapeutic regimens, especially in pediatric cases. However, patients with T-cell acute lymphoblastic leukemia (T-ALL) have a higher risk for early relapse than those with other ALL subtypes, and these cases have a substantially poorer overall prognosis . Moreover, the intense treatment regimens used can result in significant morbidity. As newer target-based therapeutic agents continue to have promising effects in many types of cancer, these principles will surely be applied to new strategies for T-ALL treatment. Recent and ongoing research continues to uncover many of the molecular and genetic aberrations that occur during thymocyte development that lead to leukemic transformation and progression.