From 1948 through 1964, 978 patients with cancer of the breast were treated by radical mastectomy alone or in conjunction with pre‐ or postoperative irradiation of the peripheral lymphatics. Since 1954 with increasing availability of skin‐sparing beams (60Co, 137Cs and electron beam), the dose to the supraclavicular and internal mammary chain nodes has been increased. This paper reviews over‐all survival rates, survival rates related to the location of the tumor within the breast and the incidence of recurrences in the regional lymphatics and the chest wall. The analysis shows a very low incidence of supraclavicular disease and a negligible incidence of parasternal recurrences. Since 1955 chest wall recurrences have also been few. It seems that one can draw the conclusion that irradiation of the peripheral lymphatics in conjunction with radical mastectomy is worthwhile except for small tumors located in the outer quadrants with the axillary nodes negative in the surgical specimen.