To determine if hip fracture incidence rates are greater in urban than in rural areas of the United States, as they appear to be in Scandinavia, we undertook a study in Olmsted County, Minnesota. During the decade 1980-89, the age- and sex-adjusted incidence of proximal femur fractures among urban residents of the central city of Rochester was 36 percent greater than among residents of the rural remainder of Olmsted County. The difference was almost entirely accounted for by an excess of fractures due to moderate trauma in elderly urban women. These first detailed results from the United States confirm earlier observations from Scandinavia that hip fracture rates are lower in rural areas.