Clinical and electrophysiological features in 43 children with acute inflammatory demyelinating polyradiculoneuropathy (AIDP) were retrospectively studied. More than one-third of these children were less than 3 years old. Some distinctive clinical features specific to adults or to children were identified. Initial symptoms such as ataxia and severe limb or back pain were more frequent in children. By using the criteria suggested here, according to our neurophysiological findings, the diagnosis of AIDP could be proposed as early of the first days of illness in 90% of the children and is confirmed during the second week. The neurophysiological evolution was very similar in children and adults except that recovery occurred sooner in children. Prognosis was better in childhood (complete recovery in all but 2 patients with minor disabilities).