A combined retrospective and prospective study of a patient population with either or both biopsy and angiographic evidence of systemic necrotizing vasculitis was undertaken in order to delineate the neurologic manifestations of this syndrome. The type, extent and natural history of the lesions in the peripheral and central nervous system were evaluated, together with the response fo the nervous system disease to corticosteroids or cytotoxic agents or both. In 60 percent of the patients, there was involvement of the peripheral nervous system. Four patterns of neuropathy were seen: mononeuritis multiplex, extensive mononeuritis, cutaneous neuropathy and polyneuropathy. The central nervous system was involved in 40 percent of the patients, manifested predominantly by diffuse and focal disturbances of cerebral, cerebellar and brain stem function. This study demonstrates the complexity and heterogeneity of the neurologic complications of the systemic necrotizing vasculitides. With treatment of the vasculitic process and prevention of further insult, both the peripheral and central nervous system make significant, and at times, dramatic, recovery.