Eighty-three episodes of osteoradionecrosis are reported. Of those episodes affecting the mandible (78), 23 (29.5%) required radical resection. The most common precipitating factors were postradiation extractions (22/83), periodontal disease (19/83), and preradiation extractions (17/83). Those episodes initially located within the zone of attached mucosa fared well with conservative measures while those initially located beyond the zone of attached mucosa fared poorly. In bone necroses where the external radiation dose to the affected bone exceeded 7,000 rad, the mandibular resection rate was high (44%). The most effective way of resolving advanced bone necroses was achieved with a course of hyperbaric oxygen therapy combined with a surgical sequestrectomy.