We report the results obtained with plasma exchange (PE) in 26 patients (18 males, 8 females) with Guillain-Barré Syndrome (GBS) of maximal severity and also the results with IVGG in 7 patients (3 males, 4 females) where PE could not be employed. A complete clinical and neurophysiological evaluation was carried out. A follow-up was effected at regular intervals for a year. From this study the efficacy of PE in GBS was confirmed and a correlation was found between the amplitude of the muscular potential registered in the acute phase and the prognosis of the illness. PE is not effective for patients with a fulminant course and blocking of conduction. Good results have been obtained with IVGG therapy, which seems to be safe and effective whenever PE is not possible.