Intrathecal administration of methotrexate(IT-MTX) has constituted the standard approach to prophylaxis and treatment of central nevous system(CNS) leukemia. We experienced a quadriplegia and motor aphasia in a 14-year-old boy following repeated IT-MTX for the prophylaxis of meningeal leukemia. He was diagnosed as ALL without CNS involvement and treated by CCG- 1882 protocol. IT-MTX was administered for CNS prophylaxis. The patient began complaining of urinary incontinence, motor aphasia and weakness in his right leg from 12 days after the 5th dose of the IT-MTX therapy. Even though the IT-MTX was discontinued, loss of muscle power progressed upward resulting in quadriplegia. The patient showed slow and partial recovery on right extremities over 3 months. We report this case with brief review of literature.