The use of bone densitometry, by dual energy x-ray absorptiometry, allows the identification, at an early stage, of subjects who will, 15-20 years later, present a fracture event. Furthermore, this technique is the most appropriate to confirm the efficacy of preventive or curative therapeutic approaches of osteoporosis. A balanced utilisation of biochemical tests is mandatory to exclude a secondary cause of osteoporosis, to help in the choice of the most appropriate therapeutic strategy and to evaluate the early response of patients to the administered drugs.