Peripheral neuropathy is increasingly recognized in patients with AIDS as well as AIDS-related complex (ARC). Thirty homosexual men with polyneuropathy were evaluated in this study. Twenty-one had ARC and nine had AIDS. We observed three distinct clinical syndromes: distal sensorimotor polyneuropathy, chronic inflammatory demyelinating polyrediculoneuropathy (CIDP), and mononeuropathy multiplex. Circulating antibodies to peripheral nerve tissues were found in all patients. In six patients, treatment with plasma exchange was undertaken because of severe, progressive weakness. Four patients with clinical, electrophysiologic, and histologic evidence of CIDP improved with plasma exchange, three regaining normal function. These results suggest that the peripheral neuropathy associated with ARC and AIDS is immunologically mediated and that plasma exchange is an effective treatment in a subgroup of patients with this disorder.