The Stewart-Treves syndrome is the most dangerous complication of chronic lymphedema following mastectomy. Prognosis is poor. In the world literature 278 cases are described. At the Surgical Clinic of the University of Heidelberg 3 cases of Stewart-Treves syndrome have been treated so far. Decisive for the prognosis of this fast growing tumor of high malignancy is early detection and initiation of therapy. The only curative therapy seems to be radical surgery in the form of interthoracic scapular exarticulation of the arm at an early stage of this disease. Radio- and chemotherapy offer palliation in advanced tumor stage.