Radiation therapy, using both external beam and brachytherapy, is one of the mainstays of treatment for oral cavity cancers. For early lip, tongue, and floor of mouth lesions, radiation alone is highly effective and produces an excellent functional result. More advanced lesions are frequently treated with combined therapy or radiation alone with surgical salvage. Buccal mucosa and gingiva lesions are generally treated with surgery but can be managed by radiation therapy if they are early. More advanced lesions are treated by surgery plus postoperative radiation. Retromolar trigone lesions can be managed by radiation alone if they are small, but larger lesions are generally treated by combined therapy. Clearly, the goal of treatment of squamous cell cancer of the oral cavity is cure of the disease with optimal function results. These goals can be achieved only by cooperative interdisciplinary evaluation and management by the surgeons, radiation oncologists, and dentists involved in the care of these patients.