BACKGROUND Vincristine is an antimitotic agent used for treatment of leukemia, lymphomas, and cancers. Its main side effect is a dose-related, length-dependent (LD) axonal neuropathy. METHODS We performed electrodiagnostic (EDx) examinations in 17 children who had been treated with vincristine and who presented with the clinical picture of a peripheral neuropathy. RESULTS The mean dose of vincristine was 8.5 ± 4.0 mg/m(2) . Clinical motor symptoms were more frequent and more severe than sensory ones. Thirteen children presented with a motor deficit, 4 of whom could no longer walk. EDx examination showed an axonal neuropathy with a non-length-dependent (NLD) pattern in 9 children and an LD pattern in 8. A major motor predominance was encountered in 12 patients. CONCLUSIONS The electrophysiological and clinical motor predominance described differs from the mainly sensory neuropathy reported in adults. Incomplete myelination due to young age may have resulted in greater sensitivity of some nerves to neurotoxic agents.