Using the unique data resources of the Rochester Epidemiology Project, we identified the residents of Olmsted County, Minnesota, who underwent total hip arthroplasty (THA) between 1969, when this technique was introduced, and 1990. During this period, 735 residents underwent 859 primary THAs. An initial dramatic upsurge in utilization of THA soon after its introduction was followed by a lower rate of increase, to an age- and sex-adjusted rate of 59.9 per 100,000 person-years in 1987 through 1990. In Olmsted County, the procedure was used more often in women than in men, but men underwent THA at a younger age than did women. THAs were performed for various conditions of the hip, but the increased utilization during the last decade of the study was mainly attributable to its application in primary degenerative hip disease among patients (male more often than female) from a wider age range; utilization of THA for hip fractures decreased during the study period. Most THAs were of the cemented variety (86.1%); however, the rate of use of noncemented THAs, first performed in 1984, is increasing. The overall upward trend in Olmsted County was consistent with European data but less than the rate of increase observed for the United States as a whole between 1983 and 1987. Olmsted County utilization rates, if projected nationally, suggest a need for more than 139,000 primary THAs each year at an annual direct cost of more than $2.7 billion. An urgent need exists for detailed examination of national utilization patterns and clarification of the role of cementless implants and of THA for hip fractures.