Osteonecrosis of the jaw (ONJ) has been noted to occur in patients with cancer receiving bisphosphonate therapy and may also be referred to as bisphosphonate associated osteonecrosis (BON). ONJ has come to attention through case reporting and the pathogenesis and true incidence of this condition are not yet defined. ONJ appears to be a relatively uncommon event, but it is of clinical significance; the evolving data on ONJ are discussed here.