The osteonecrosis of the jaw is a new emergent disease, secondary to prolonged use of bisphosphonates. Bisphosphonates are a class of drug used in prevention and cure of bone diseases such as malignancy or bone metabolic diseases. In this article, we have tried to summarize, for patients taking IV or oral bisphosphonates-therapy, the most important informations on the pathogenesis and the risk factors in osteonecrosis of the jaw with particular attention about the preventive policies.