This is an analysis of 304 patients with invasive, previously untreated T1-T2 squamous cell carcinoma of the glottic larynx treated with radiation therapy at the University of Florida between October 1964 and December 1984. All patients had a minimum 2-year follow-up and 82% had at least 5 years of follow-up. Patients were excluded from the analysis of local control if they died within 2 years of treatment with the primary site continuously disease-free; all patients were included in the analysis of treatment complications. Patients were staged according to the 1983 AJCC system. Stage T2 was subdivided into 2 groups as follows: T2a (normal mobility) and T2b (decreased mobility). The rates of local control with radiation therapy were as follows: T1, 159/171 (93%); T2a, 50/65 (77%); and T2b, 31/43 (72%). Patients were further divided into subsets based on T stage and the surgical procedure that would have been required to resect the lesion. Local control was noted to improve with higher doses and dose per fraction in 4 of 7 subsets. In 2 of 3 subsets where a dose-fractionation relationship was not observed, there were no local recurrences in 1 subset and only 2 local recurrences in the other. The overall incidence of serious complications was 5/304 (1.6%) and was associated with T stage and with increasing total dose and dose per fraction.