Lymphodepletion chemotherapy followed by infusion of T cells that are genetically modified to express a chimeric antigen receptor (CAR) targeted to CD19 is a promising and novel therapy for patients with relapsed and/or refractory B cell acute lymphoblastic leukemia, non-Hodgkin lymphoma, and chronic lymphocytic leukemia. Identification of factors that govern outcomes after CAR-T cell immunotherapy has been hindered in part due to the functional heterogeneity of infused CAR-T cell products. We are conducting the first clinical trial in which CD19 CAR-T cells are manufactured from distinct subsets of T cells and formulated in a defined composition for infusion to patients with B cell malignancies. Clinical responses, toxicities and factors governing outcomes will be presented.