Using the data resources of the Rochester Epidemiology Project, we carried out a descriptive study of fracture incidence among the residents of Olmsted County, Minnesota. During the 3-year period 1989-91, 2901 County residents > or = 35 years of age experienced 3665 separate fractures. The age- and sex-adjusted (to 1990 United States whites) incidence of any fracture was 2205 per 100,000 person-years (95% CI, 2123 to 2286) and that of all fractures was 2797 per 100,000 (95% CI, 2705 to 2889). Age-adjusted fracture rates were 40% greater among women. Incidence rates increased with age in both sexes. One-third of the fractures involved the hip, spine or distal forearm - the skeletal sites traditionally associated with osteoporosis. The age- and sex-adjusted incidence of fractures due to moderate trauma (2205 per 100,000 person-years; 95% CI, 2106 to 2303) was twice that of fractures due to more severe trauma (1164 per 100,000; 95% CI, 1106 to 1223) and 12 times that of pathological fractures (178 per 100,000; 95% CI, 133 to 222). Overall fracture rates were 15% greater among residents of the central city of Rochester compared with the rural portion of Olmsted County. The incidence of limb fractures among Rochester residents was 14% higher than comparable rates documented for this community 20 years earlier in 1969-71, due mainly to a substantial increase in the incidence of leg fractures.