Vincristine (VCR) is a fundamental component of various chemotherapy protocols. Several reports of accidental intramuscular (i.m.) administration or overdose of VCR have been published in the medical literature. We report on an uneventful clinical course of both i.m. and overdose of VCR in a 6-year-old girl with Wilms' tumor. To prevent the administration of overdosed drug by the i.m. route accidentally, chemotherapy should be administrated only by experienced medical doctors.