Plasmapheresis modifies the course of the acute Guillain-Barré syndrome (GBS) in terms of time-related parameters such as time on a respirator or time to achieve a specific area of improvement at specific times after onset of the illness such as at 1 month and at 6 months. Certain factors are associated with poorer outcomes in acute GBS. These include amplitude of compound muscle axon potentials on stimulating distally, time of onset of disease of 7 days or less, need for ventilatory support, and older age. Plasmapheresis, the only variable that the physician can influence, has a beneficial effect over and above all these factors.