Osteoradionecrosis is a severe complication of radiation therapy for cancer. Prevention of osteoradionecrosis is most important as the condition may be chronic, progressive and lead to pathologic fracture. The clinical experience at the Cancer Control Agency of British Columbia with 26 cases in approximately 1000 patients treated with radical radiation therapy to the head and neck region is presented and discussed. A clinical classification system is proposed to provide a guide for treatment selection, and to allow classification for research purposes.