The authors investigated whether T cells have a role in the pathogenesis of axonal polyneuropathy and monoclonal gammopathy by comparing the presence of T cells in sural nerves of 23 patients with axonal polyneuropathy and monoclonal gammopathy (12 IgM, 11 IgG), of 15 patients with chronic idiopathic axonal polyneuropathy, and of 10 autopsy cases. Seven patients with an increased T-cell density had a progressive disease course, and four of these patients were treated with prednisone with a good response, suggesting that vasculitis plays a role in the pathogenesis.