It is important to recognize osteonecrosis of the jaws in patients treated with bisphosphonates because an early diagnosis can make a significant difference to the outcome of the disease. The aim of this study is to describe the radiological features of bisphosphonate osteonecrosis (BON) in order to aid its prompt recognition.A conventional radiograph, a computed tomograph (CT), a magnetic resonance image (MRI) and a 99Tc(m)-MDP 3-phase bone scan were carried out for 11 patients with BON. The main imaging findings of osteonecrosis are described.Conventional radiography and CT displayed osteolytic lesions with the involvement of cortical bone. MRI demonstrated the characteristic features of osteonecrosis and the oedema of soft tissues. Both CT and MRI were very useful in defining the extent of the lesions. 99Tc(m)-MDP three-phase bone scan was the most sensitive tool to detect the osteonecrosis at an early stage.99Tc(m)-MDP three-phase bone scans who could be used as a screening test to detect subclinical osteonecrosis in patients who have received bisphosphonates. CT scans and MRI are useful in defining the features and extent of osteolytic lesions.