Peripheral neuropathies cause weakness and sensory loss that can produce severe disability. Some neuropathies are immune-mediated and associated with antibodies. It has been postulated that Rituxan treatment may reduce the level of antibody production limiting the loss of muscle strength and hence improve activities of daily living. The purpose of this open-label study (all participants get Rituxan and not placebo) is to determine the safety and effectiveness of Rituxan in the treatment of polyneuropathies associated with serum IgM autoantibodies in those who have already been treated with one course of Rituxan. Subjects will be treated on the in-patient Clinical Research Center with Rituxan for two treatments one week a part and then individual treatments every 10 weeks for one year. The effectiveness of Rituxan will be followed by looking for increases in muscle strength and decreases in the serum IgM autoantibodies.