Background: Methotrexate (MTX) is a cornerstone of therapy for pediatric patients with acute lymphoblastic leukemia (ALL). Administration of high dose (HD) MTX requires hospitalization and concurrent intravenous fluids and leucovorin while awaiting drug excretion. HDMTX has been associated with acute adverse events (AEs), such as mucositis, neurotoxicity, and myelosuppression, that can impact quality of life and ability to administer subsequent chemotherapy. There are limited data evaluating differences in AEs after HDMTX among demographic groups.