 11. Known active central nervous system CNS leukemia, as defined by unequivocal morphologic evidence of lymphoblasts in the cerebrospinal fluid CSF, use of CNS-directed local treatment for active disease within the prior 28 days, symptomatic CNS leukemia i.e., cranial nerve palsies or other significant neurologic dysfunction within 28 days. Patients may have history of CNS leukemic involvement if definitively treated with prior therapy and no evidence of active disease defined as 2 consecutive spinal fluid assessments with no evidence of disease at the time of registration. Prophylactic intrathecal chemotherapy is not a criterion for exclusion. 