Osteoporosis and subsequent fractures is a rapidly growing major health problem in many parts of the world. Even if prevalence and incidence are high in Europe, rate of increase is even higher in Asia. The majority of fractures occur in women underlining the importance of ovarian deficiency. Genetic factors and lifestyle greatly influence the incidence and prevalence both in men and women and the importance of estrogen deficiency at ages over 85, where a large number of fractures actually occur, may well be questioned. Among several risk factors the amount of bone mass remains crucial. Several techniques adequate in accuracy and precision exist to determine bone mass. The costs for these measurements are not negligible. Several pharmacologic regimens look promising for the prevention of osteoporosis and indeed for treatment of established osteoporosis. However, long-term data and clinical experience are warranted prior to establishing these pharmacological tools in the field of osteoporosis. For HRT and ERT such data are available. ERT and indeed HRT may halve the risk of osteoporotic fractures in women at least in current users. The effect at least on bone mass wears off after discontinuation of treatment but is never totally lost. In the interest of health care costs it is suggested that HRT could be started 15-20 years after the menopause and still provide protection for subsequent fractures.