T HE radical surgical treatment for potentially curable rectal carcinoma continues to produce relatively modest long-term survival results. Gilbertsen9 points out that although improvement in general medical care, anesthesia, and sur- gical techniques have significantly altered the survival, the gain has been a modest io per cent when the seriesof 1940-1950 are compared to 1951-1959. Morson and Bussey'3 more recently in their review of 1,596 cases, conclude that "surgery alone has little more to offer in the treatment of rectal cancer . . . in spite of all attempts at earlier diagnosis, there has been no significant change in the incidence of the different stages of rectal cancer over the past 25 years." A greater improvement in survival might be mediated through some conceptual change in management. Good radiobiologic evidence has led to interest in preoperative irradiation as a method with the potential to improve sur- vival even in lesions which in the past had been considered primarily surgical prob- lems. One can expect small groups of cells to be more readily destroyed by radiation therapy than large masses because the former are relatively well oxygenated and, therefore, relatively radiosensitive. Also, it has been shown, both in the laboratory and in human experience, that smaller tumors containing fewer cellsare more readily de- stroyed than larger masses. Stearns and co-workers,'7 Ruff and co- workers,'5 and Fletcher and associates7 have used preoperative irradiation either with orthovoltage or supervoltage roentgen rays. Stearns, Deddish and Qua&7 be- lieved that there was significant improve- ment in survival in those patients given preoperative irradiation who were sub- sequently classified as Dukes C,4" those in whom regional lymph nodes showed histologic evidence of tumor. In none of these reported studies had randomized controls been used. Furthermore, in the reported works the volume of tissue treated was variable and in none was the treat-