This study is a retrospective analysis of 134 patients treated with radiotherapy at our hospital. The sample included 88 stage T1 and 46 stage T2 patients. Sixty-two patients had anterior commissure involvement, 37 patients had impaired vocal cord mobility, and 24 patients had supraglottic or subglottic extension. Irradiation was given, with the dose ranging from 60 to 72 Gy. Laryngectomy was the main salvage treatment for local recurrence. The 5-year initial and final local control rates were 71% and 83%, and the 10-year initial and final local control rates were 69% and 80%, comparable to the results of other series. The 5-year rate of overall survival with final larynx preservation was 77%. Multivariate analysis revealed that anterior commissure involvement is prognostic of a poor outcome in patients with T1 glottic cancer. Further subgroup analysis revealed that a fraction size of > 200 cGy could overcome the negative impact of anterior commissure involvement and significantly improve the 5-year local control rate in T1 patients (100% at > 200 cGy versus 45% at < or = 200 cGy; p = .04). Subglottic extension of the glottic cancer predicted poor outcome in T2 patients. The 5-year local control rates of patients with and without subglottic extension were 9% and 77%, respectively (p < .001). According to our results, radiotherapy with a fraction size of > 200 cGy is recommended for T1 disease with anterior commissure involvement. For patients with T2 disease and subglottic extension, radiotherapy alone produces poor results. Further improvement of outcomes by other treatment strategies needs to be investigated.