The average annual incidence of Guillain-Barré syndrome is 1.5 per 100 000. Mortality was about 5% in a recent clinical trial. Ten percent of patients have severe neurological sequelae one year after onset. For these patients, general care is essential and should be provided in appropriate hospital units. Corticosteroids, administered orally or intravenously are ineffective. Plasma exchange (PE) was the first treatment to demonstrate efficacy in randomized clinical trials. Indications have been recently specified. Patients who can walk must be given two PEs and two additional PEs in case of aggravation. Four plasma exchanges are sufficient in patients unable to walk unaided (intermediate form) or who are mechanically ventilated (severe form). No further PE is required if the patient fails to improve. High-dose intravenous immunoglobulins (0.4 g /kg daily for 5 days) and PE have equivalent efficacy in intermediate and severe forms. The optimal dose of IVIg and the number of Pes in the different severity forms are being assessed in an ongoing study.