Plasma exchange has proven to be effective in diseases of established or presumed autoimmune etiology as well as in hyperviscosity syndromes and some rare metabolic disorders. Its application is thought to be relatively safe; nevertheless, severe complications may occur. We therefore analyzed the complications of 291 exchanges in 39 patients with neurological diseases. Minor complications developed in 4.8% and major complications in 2.7% of procedures, including one death. Severe infections and technical problems have been the most serious side effects, sometimes followed by organ failure or even death.