Over the 20-year period from 1965 to 1984, 370 residents of Rochester, Minnesota experienced 402 femoral fractures exclusive of the hip, giving an overall incidence rate of 37.1 per 100,000 person-years (95% confidence interval, 33.4-40.8). Of these, 54 were subtrochanteric and 210 were diaphyseal, while 123 involved the distal femur and 15 were at unspecified femoral sites. Fifty-eight percent of these fractures were caused by severe trauma. The incidence of femoral fractures due to severe trauma was greatest in young patients, especially for diaphyseal fractures, and showed a male excess. One-third of the fractures were associated with moderate trauma and were responsible for the rising incidence rates with age at all three fracture sites. These increases were greater in women. Eighty percent of patients 35 years of age or older with fractures due to moderate trauma had prior evidence of generalized osteopenia or a condition likely to cause localized osteopenia in the fractured femur. These data confirmed similar findings from Sweden, providing evidence for a relationship between osteoporosis and femoral fractures distal to the hip.