Bisphosphonates are widely used drugs, primarily for osteoporosis and also in oncology. A drug-induced side effect or complication, which only recently came to light in 2003, is osteonecrosis of the jaw. This study reviews the chemical characteristics of the various bisphosphonates, their possible mechanism of action, relative potency, the commercial products available on the spanish pharmaceutical market and the indications for bisphosphonate treatment. The study also considers osteonecrosis of the jaw with regard to its onset, concept, clinical stages, why this pathology affects the jaws, its risk factors, incidence, the attitude to be adopted by dentists with patients taking bisphosphonates, a quick review of the treatment and the possible prediction of osteonecrosis.