Here we report the first case of peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), who initially presented with peripheral neuropathy. Nerve conduction, cerebral spinal fluid studies and his clinical course were compatible with sub-acute demyelinating polyradiculoneuropathy. In addition, left cervical lymph node swelling was observed on admission. Diagnosis of PTCL-NOS was made by the histological, immunohistochemical, and Southern blot analyses on the biopsy specimen from the enlarged lymph node. Combination chemotherapy composed of cyclophosphamide, vincristine, doxorubicin and prednisolone (CHOP) was effective for polyneuropathy as well as for lymphoma. Several antibodies relating to paraneoplastic syndrome such as Ma1, Ma2, Amphiphysin, CV2, Ri, Yo and Hu were all negative. Because sural nerve biopsy performed prior to CHOP therapy revealed no infiltration of lymphoma cells, immune dysfunction mediated by some cytokine or unidentified autoantibody related to PTCL-NOS was thought to be involved in the polyradiculoneuropathy.