A 49-year-old womanwith diabetes mellitus developed progressive weakness and atrophy of both thighs rendering her wheelchair-bound within two months. The neurological findings and electrophysiological test results were compatible with diabetic amyotrophy (DA). Immediately after intravenous immunoglobulin (IVIg) therapy (20 gx3 days), she becameable to walk with a cane. After the next course of the therapy, she could walk without assistance. This dramatic effect of IVIg therapy together with the recent observation of vasculitic neuropathy in DAindicates an inflammatory process in this condition, and gives support to this treatment for DA. (Internal Medicine 40: 349-352, 2001)