INTRODUCTION. High-dose methotrexate (MTX) has showed to increase the surveillance in children with acute lymphoblastic leukemia and other neoplasms. However, MTX may induce significant neurotoxicity. AIM. To evaluate, in our population of patients who have been treated with MTX, the incidence of neurotoxicity and to describe its main clinical and radiological characteristics. PATIENTS AND METHODS. We retrospectively review the patients who received treatment with systemic high-dose MTX and/or intrathecal MTX between 1994 and 2010. The children who presented clinical o radiological signs of neurotoxicity were reviewed. RESULTS. We identified 284 patients who received high-dose intravenous and/or intrathecal MTX. 9 patients presented neurotoxicity. The median age at diagnosis was 6 years; 6 patients were male. The diagnosis included: 6 acute lymphoblastic leukemia, 2 medulloblastoma and 1 lymphoma. 66% patients presented focal neurological dysfunction, 3 had non-specific symptoms. In 5 patients the symptomatology started the first 14 days after the MTX administration. 8 patients had complete clinical resolution, but only one presented neurological long term effects. All the patients except one showed signs of acute leukoencephalopathy in the brain MR study. These alterations resolved one year later in 3 patients; in the other patients the MR alterations persisted. The neurotoxicity management was corticosteroid, folinic acid, aminophylline and dextromethorphan. CONCLUSION. The MTX neurotoxicity it can present as acute or chronic. It has a wide clinical spectrum, ranging from sub-clinical manifestations with complete recovery to a chronic and progressive encephalopathy.