In this study, we will combine G-CSF as priming prior to and during the administration of salvage chemotherapy regimen in ALL. Abundant data suggests that leukemic cells receive key growth and survival signals from the bone marrow microenvironment. Our preclinical data show that 4-5 days of G-CSF treatment is associated with a loss of osteoblasts and decreases expression of key chemokine/ cytokines which support lymphocyte development. The investigators hypothesize that G-CSF will disrupt the protective effects of the bone marrow microenvironment and augment the effect of chemotherapy in adults with ALL. This is a pilot study of G-CSF priming in adult patients with relapsed or refractory ALL to determine the feasibility and to characterize the effect of G-CSF treatment on the marrow microenvironment.