Inflammatory demyelinating polyradiculoneuropathy, especially in its acute form (the Guillain-Barre syndrome) is often the cause of flaccid pareses. Etiology of this immunological condition is frequently unknown. In severe forms of the disease good therapeutic effects may be obtained with plasmaferesis or intravenous injections of human immunoglobulin. The monitoring of respiratory and vascular sufficiency is most important, and so is symptomatic treatment. In justifiable cases immunosuppressive medication may be applied.