The incidence of head and neck cancer increases annually in the United States, and radiation therapy is frequently a primary or adjunctive mode of therapy. As the number of radiotherapy patients rises, the need for proper detection, diagnosis, and treatment of oral lesions likewise increases. Depending on tumor site and size, radiation dosage, and preexisting oral conditions, a variety of oral radiation side effects may be present. These range from mild and reversible changes to severe and potentially disfiguring or life-threatening alterations. This article, in two parts, will review the oral manifestations of cancer radiation therapy and appropriate management techniques.