The epidemiology of pelvic fractures was investigated in Rochester, Minnesota, residents during the decade 1968 to 1977. The overall incidence was 37 per 100,000 person-years, substantially higher than previous population-based studies would indicate. The incidence increased markedly with age in both sexes, and was greater for women than men at all ages over 35, reaching a maximum incidence of 446.3 per 100,000 person-years in women 85 or older. Half of all pelvic fractures were attributed to moderate trauma, usually a fall from standing height, 95% of which were minor (Type I or II). Moderate trauma was responsible for the increase in pelvic fracture incidence with age in the high-risk population of postmenopausal women. A large proportion of both men and women with moderate trauma fractures had some evidence of preexisting osteoporosis.