Multiple sclerosis (MS) was believed to be an autoimmune disease of central nervous system (CNS). Recently, several studies showing early involvement of peripheral nervous system (PNS) in MS pathological process have been published. This review own analyzer and published clinical and paraclinical data on PNS pathology in MS patients and CNS damage in patients with chronic inflammatory demyelinating polyneuropathy. Different mechanisms of the damage of PNS may explain different clinical manifestation of PNS involvement in MS.