Professor Urist's contributions to the understanding of osteoporosis are worthy of reevaluation at this time, when interest in the field has reached unprecedented heights. Recent advances in technology have greatly increased our understanding of osteoporosis by showing that there is no loss of bone in normal premenopausal women, and that the loss which starts at the menopause can be attributed to an increase in bone resorption. It is suggested that the primary event is a rise in plasma calcium that leads to a rise in obligatory urinary calcium loss, which in turn increases the calcium requirement. The subset of the postmenopausal population who develop fractures (particularly in the spine) show additional risk factors, which include malabsorption of calcium (which further increases bone resorption) and reduced adrenal androgen production (which may produce a fall in bone formation). The treatment of established cases requires control of bone resorption by calcium supplementation and/or hormone therapy, with the addition of calcitriol if malabsorption of calcium is present. Stimulation of bone formation is more difficult, but there is a suggestion that this may be possible with the use of anabolic steroids.