This study reviews 11 cases of retroperitoneal tumors. The authors note the absence of symptoms and recommend preoperative angiography as a method of diagnosis and therapy. Preoperative vascular embolization of the retroperitoneal mass helps to control bleeding at operation. Operative results were disappointing. Although three patients are still alive some ten years after treatment, four have died of the cancer itself, meanwhile. But even in the case of very invasive tumors, the results may seem satisfactory for fairly long periods of time.