SummaryThe classical distinction between postmenopausal and senile osteoporosis still has some validity. Vertebral body fracture (postmenopausal osteoporosis) presenting clinically with severe back pain is uncommon, but requires treatment to reduce the risk of further fracture; asymptomatic vertebral body collapse is common (20 per cent prevalence in one survey). Fracture in old age with minor trauma (senile osteoporosis) affects most sites in that the risk of fracture is related to bone mineral density, but hip fracture has by far the greatest clinical and public health importance. Preventive strategies can significantly reduce fracture risk. Important population strategies include exercise, smoking cessation and hormone replacement therapy (if maintained for a long period). Institutionalised or infirm elderly people constitute a high risk group; the avoidance of immobility is important and vitamin D supplementation may be. The selective use of interventions in a minority of the population identified by measurement of bone mineral density will have little impact on the incidence of hip fracture-it is too poor a screening test.