Vincristine is a vinca alkaloid used in combination with other agents in the treatment of solid tumors, lymphoma, and leukemia, as well as for idiopathic thrombocytopenic purpura and autoimmune hemolytic anemia. A dose-limiting complication of vinca alkaloids is neurotoxicity. Vincristine is the oldest and also the most neurotoxic agent in this group. Described here is the case of a 4-year-old girl with unilateral palpebral ptosis. She has been diagnosed with precursor B-cell acute lymphoblastic leukemia. Ptosis was noted on the 45th day of therapy, and the last vincristine was administered on the 28th day of protocol 1. Vincristine-induced unilateral palpebral ptosis is a novel finding. Experience with this case suggests conservative treatment, with periodic examination, especially if ptosis is mild. (C) 2009 by Elsevier Inc. All rights reserved.