A patient with acute lymphoblastic leukaemia was mistakenly given vincristine intraventricularly, as part of an intensified course of chemotherapy. Despite a CNS washout and supportive treatment, the patient developed progressive ascending paralysis, gradually lapsed into coma and died some 10 days later. Autopsy and post-mortem histological examination showed evidence of brain death caused by florid encephalomyelitis, apparently induced by the intraventricular administration of vincristine.