Castleman's disease is a rare clinicopathological entity characterized by multicentric angiofollicular lymph node hyperplasia and sometimes associated with polyneuropathy. We report 4 cases identified with diagnosis of Castleman's disease by lymph node biopsy and peripheral polyneuropathy. They had a hypesthesia of all limbs, gait disturbance, weakness of distal lower limbs and enlargement of lymph nodes. Among them 2 patients were combined with POEMS (polyneuropathy, organomegaly, endocrinopathy, increase of M protein, skin change) syndrome. Motor and sensory nerve conduction velocities were below 70% of lower normal limit, the amplitudes of compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) were reduced. Deterioration of nerve conduction study was more severe in lower limb than the upper. More denervation potentials were found in lower limbs than the upper and in distal limbs than the proximal. As disease getting worse, the slower conduction velocity and lower amplitude of CMAP and SNAP were observed.