Chimeric antigen receptor (CAR) modified T cells targeted to CD19 have resulted in unprecedented remission rates for adult and pediatric patients with relapsed and refractory B cell acute lymphoblastic leukemia (ALL). With regulatory approval for tisagenlecleucel and many other agents under active investigation, the use of CAR T cells for ALL continues to expand. While some remissions from anti-CD19 CAR T cells are durable without a consolidative allogeneic stem cell transplantation, CD19 positive and negative relapses remain a significant concern fueling investigations into the biology of CAR T cell persistence and the development of CARTs that target more than 1 antigen. The treatment related toxicities of cytokine release syndrome and neurologic events are potentially life threatening but recent advances have improved understanding and management strategies. This review summarizes outcomes for patients with ALL treated with CD19-CAR T cells while exploring the field's challenges and future directions.