One of the most common uses of therapeutic plasmapheresis is for the treatment of immunologically mediated polyneuropathies. This paper discusses the use of plasmapheresis in Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, polyneuropathies associated with paraproteins, lower motor neuron syndromes, and polyneuropathies associated with HIV. As the pathogenesis of immunologically mediated polyneuropathies becomes better understood, newer therapies for these syndromes will evolve: however, therapeutic plasmapheresis is likely to continue to play a central role in the treatment of many of these diseases.