The prevention of hip fractures, a major cause of morbidity and mortality in the elderly, is hampered by insufficient knowledge of the population at risk. A Colles' fracture associated with minor trauma is indicative of an overall 50% increase in the risk of a subsequent hip fracture. The relative risk of a subsequent hip fracture is greater for men with Colles' fracture (RR = 6.4) than for women (RR = 1.3). Among women, the risk is increased more than twofold for those whose Colles' fractures occurred at the age of 70 or older but is not increased for younger women. That greater predictive power was not achieved may be due to differences in the pathophysiology of osteoporosis at various fracture sites.