A study of 621 patients with glottic carcinoma treated by megavoltage radiation therapy was made. The results of treatment according to the status of the mobility of the involved cord and the extent of the mucosal surface spread are presented. More than two-thirds (69 per cent) of the patients survived without disease (absolute rate) and over three-quarters (78 per cent) were cured (determinate rate) by radiation therapy alone for 5 or more years with preservation of useful voice. For lesions with normal cord mobility, the 3 year and 5 year NED rates of approximately 90 per cent were achieved. For lesions with impaired cord mobility, the 3 year and 5 year NED rates deteriorated to approximately 65 per cent. For lesions with completely fixed cord, the 3 year and 5 year NED rates were approximately 25 per cent following radiation therapy. Over two-thirds of radiation failures (70 per cent) were cured by subsequent surgery without postoperative complications. Treatment policies for this disease are outlined. Based on the status of the mobility of the involved cord and the extent of the mucosal surface spread, a modification of the TNM staging system is suggested.