Radiation therapy plays an important role in the care of patients with head and neck cancer. When the oral cavity and the salivary glands are exposed to high doses of radiation, there can be dramatic effects on the patient's oral health. The clinical consequences of radiation can include mucositis, hyposalivation, taste loss, osteoradionecrosis, radiation caries and trismus. This paper looks at the available literature regarding the effects of radiotherapy on the oral environment and outlines practical clinical approaches to prevent or reduce the adverse side effects of treatment.