Bisphosphonates offer a significant improvement in the quality of life for cancer patients; these potent inhibitors of bone resorption have been shown to markedly reduce the morbidity frequently resulting from bone metastases. Despite the success of bisphosphonates as therapeutic agents, however, toxicity in the form of osteonecrosis of the jaw (ONJ) is a rare complication whose incidence rate has climbed in recent years. ONJ is defined as an unexpected development of necrotic bone in the oral cavity, and is commonly associated with administration of the bisphosphonates Pamidronate and Zoledronate. Clinical features include local pain, soft-tissue swelling, and/or loose teeth; ONJ is also often correlated with previous dental procedures, such as tooth extractions, during biphosphonate therapy. Although additional risk factors--such as corticosteroids, chemotherapy, radiotherapy, trauma or infection?exhibit etiological associations with ONJ, the real pathobiology has not yet been fully elucidated. Here we report our findings on all 2005 OJN cases presented at our institution resulting from bone metastatic prostate cancer treated with zoledronic acid. The incidence of ONJ is nearly 3% (3 out of 104) in these patients.