Osteoradionecrosis is one of the most serious complication after heavy irradiation of bone and most particularly following treatment of cancers within the head and neck. The irradiated bone has the decreased vascularity and is easily infected. As a result, the spread of infection may cause a nonhealing wound that is very difficult to be treated. A comprehensive prophylactic dental care as well as proper blocking of the radiation field before radiotherapy must be considered to reduce the risk of osteoradionecrosis. We present three cases of osteoradionecrosis which developed after extraction of teeth in irradiated patients.