The pathogenesis of lymphedema of the upper extremity following a radical mastectomy is not as yet completely understood. A conspicuously swollen arm may be the only noticeable evidence of a radical mastectomy. Rarely a lymphan-giosarcoma of the edematous arm may ensue after a prolonged period (1). Since the only known treatment of the condition is its prevention, we have been encouraged to investigate this problem. Our interest was stimulated by a patient in whom thrombophlebitis of the veins of the forearm occurred following a radical mastectomy. The arm was bandaged with elastoplast for a period of two months. To our surprise swelling of the arm did not develop in spite of the severe thrombophlebitis. As a result of this experience, prophylactic bandaging of the arm of all patients subjected to radical mastectomy was tried. In 50 consecutive cases in which this procedure was employed, no appreciable edema of the arm, such as could be classified as moderate or severe, ensued. The routine use of this pro...