Purpose: To review the results of primary radiation therapy for patients with T4 squamous cell carcinoma of the larynx.Methods and Materials: Between October 1964 and October 1994, 43 patients with T4 invasive squamous cell carcinoma of the larynx received radiotherapy with curative intent in the University of Florida Department of Radiation Oncology. All patients had a minimum of 2 years follow-up. There were 26 primary cancers of the supraglottic larynx, 11 of the glottic larynx, and 6 of the subglottic larynx.Results: The 5-year actuarial rate of local control was 52%. By direct calculation, local control was achieved in 8 (38%) of 21 supraglottic carcinomas, 8 (89%) of 9 glottic tumors, and 2 of 6 subglottic tumors. Local control of nonbulky lesions was achieved in 67%, and 38% of bulky lesions were locally controlled. Only 3 (17%) of 18 local recurrences were successfully salvaged by subsequent surgery. There were 2 (5%) severe complications of irradiation.Conclusion: From our series, as well as a review of the literature, local control by primary irradiation has been achieved in approximately 50% of patients with T4 laryngeal cancer. Selection factors for choosing irradiation have not been well described: the present series contains a small amount of information suggesting that tumor volume may be a reliable predictor of control, but further substantiation is required.