Osteoporosis is one of the major problems facing women and older people of both sexes. The morbid event in osteoporosis is fracture. However, the definition of osteoporosis should not require the presence of fractures but only a decrease in bone mass that is associated with an unacceptably high risk of fracture. In the USA, approximately 1.5 million fractures annually are attributable to osteoporosis: these include 700,000 vertebral fractures, 250,000 distal forearm (Colles') fractures, 250,000 hip fractures, and 300,000 fractures of other limb sites. The lifetime risk of fractures of the spine (symptomatic), hip, and distal radius is 40% for white women and 13% for white men from 50 years of age onwards. Following a hip fracture, there is a 10%-20% mortality over the subsequent 6 months, 50% of sufferers will be unable to walk without assistance, and 25% will require long-term domiciliary care. Contrary to prevailing opinion, the morbidity and suffering associated with wrist and spine fractures are also considerable. The annual cost of osteoporosis to the US healthcare system is at least $5-$10 billion with similar incidence and cost in other developed countries. These already high costs will increase further with continued aging of the population. In addition, the population explosion in underdeveloped countries will change the demography of osteoporosis; for example, the incidence of hip fracture, and, presumably, other osteoporotic fractures will increase four-fold worldwide during the next 50 years and the attendant costs will threaten the viability of the healthcare systems of many countries. Unless decisive steps for preventive intervention are taken now, a catastrophic global epidemic of osteoporosis seems inevitable.