Beside surgery and chemotherapy, which has recently become important, radiotherapy is an efficacious means in the treatment of oral cavity cancer, both when applied alone and in combination. Clinical radiotherapy is based on the differences in sensitivity between normal tissue and tumor. The radiosensitivity of oral cavity cancers--above all squamous cell carcinoma--may even be considered to be mediocre: therefore a dose should be reached in order to destroy the malignant growth. In percutaneous radiotherapy orthovoltage is without any prospects; high-energy methods, above all telecobalt, have certain advantages, particularly the lower absorption in the bones. In "brachytherapy" we prefer the artificial nuclides 137Cs and 60Co instead of 226Ra for moulds and 198Au grains for interstitial application. At first the radiotherapist has to decide whether to advise radical or palliative treatment. Patients with secondary nodes in whom "radical surgery is inadvisable should have radical radiation therapy..." (Gibb and Todd) in a dose of nearly 5000 rads. Radiotherapy after an inradical neck dissection is burdened with a therapy before surgery can be considered in select cases. The treatment of oral cavity cancer should be practiced in close cooperation between the surgeon and the radiotherapist.