Today, bone density can be measured by different technical methods which show variations in terms of reproducibility, accuracy and sensibility. A crucial parameter is the reproducibility, which differs considerably from method to method. With densitometric methods it is possible not only to evaluate patients at risk getting an osteoporosis but also to establish an individual prophylaxis and therapy by means of highly precise quantitative methods, based on the parameters 'bone density' and 'loss of bone density'. A high bone turnover leads to fast bone loss and, vice versa, fast bone loss, measured by densitometry, is correlated with high bone turnover in postmenopausal women. This allows to establish an individual therapy with antiresorption resp. bone-stimulating agents and the knowledge about a tailored, individual treatment increases patients' compliance and reduces the rate of 'non-responders'.