Polyneuropathy associated with anti-MAG monoclonal IgM gammopathy is responsive of mainly a sensory deficit in predominantly males ,aged 40-70 years. Significantly high serum anti-MAG antibodies are linked with demyelinating features of the peripheral nerves.Rituximab, an anti-CD 20 monoclonal antibody is a new drug which reduces B-lymphocytes. This study will test the safety and efficacy of rituximab in the treatment of patients with anti-MAG polyneuropathy.