Seven diabetic patients developed a progressive, moderately severe, motor rather than sensory neuropathy predominantly affecting the legs. This met clinical and electrophysiological criteria for chronic inflammatory demyelinating polyneuropathy (CIDP). Nerve biopsies showed a variety of abnormalities, none of which clearly distinguished between diabetic polyneuropathy and CIDP. The patients were treated with combinations of corticosteroids, azathioprine, plasmapheresis and intravenous immune globulin; all improved substantially. We believe that CIDP may masquerade as unusually severe and progressive diabetic distal symmetric polyneuropathy. It is important to recognize CIDP in diabetics because, unlike diabetic polyneuropathy, CIDP is treatable.