This is a retrospective analysis of 185 patients with squamous cell carcinoma of the tonsillar region treated at the Department of Radiation Oncology, University of Maryland Hospital from 1956 to 1977. All patients were treated by one of the following: (1) external beam therapy alone; or (2) combined external beam and interstitial brachytherapy. Five-year disease-free survivals, for early Stages (I and II), are 100% and 73%, comparable to the other series published in the literature. However, in advanced Stages III and IV, survival data showed 52% and 21%, respectively, 5-year disease-free survival better than any other reports. It is thought that the special interest of the authors in interstitial brachytherapy and a well-integrated plan of external beam and brachytherapy is responsible for this success. The local control rate for T1, T2, T3, and T4 was 94%, 88%, 62%, and 19%, respectively, with the overall regional control rate of 83%. The prognostic factors appear to be related to the T-factor, N-factor, radiation dose, and method of treatment given, and the degree of tongue involvement. The detailed analysis of survivals and failures in the light of dosimetric study is presented along with some example cases of interstitial brachytherapy.