The objective of this study was to evaluate whether electroneurography could help in differentiating between vincristine-induced neuropathy and acute inflammatory demyelinating polyradiculoneuropathy. We performed electroneurography in 7 children from September 2006 to March 2009 admitted to receive chemotherapy including vincristine for acute lymphoblastic leukemia, in whom severe acute limb weakness developed, suggesting vincristine-induced neuropathy. Three of 7 patients had electroneurography, suggesting acute inflammatory demyelinating polyradiculoneuropathy. They received intravenous immunoglobulins without discontinuing chemotherapy, and within 10 days their electroclinical conditions improved. Although electroneurography showed only absent F waves, preventing us from reaching a definitive neurophysiological diagnosis of acute inflammatory demyelinating polyradiculoneuropathy, children's presenting clinical manifestations, their disease course, and rapid and complete recovery after intravenous immunoglobulins argued strongly in its favor. A prompt, correct differential diagnosis of vincristine neuropathy and acute inflammatory demyelinating polyradiculoneuropathy in patients with acute lymphoblastic leukemia receiving vincristine is essential to improve disease outcome and prolong life expectancy.