During the 10-year period 1981-90, 1752 primary total hip arthroplasties were performed in the County of South Jutland, Denmark. The annual number increased to a steady state during 1988-90. In this period, the incidence was highest in the age group 70-79 years for both women and men, with 485 and 410 arthroplasties per 100,000 inhabitants, respectively; the overall incidence was 82 per 100,000 inhabitants. During the next 30 years, the demand for primary hip arthroplasties in Denmark is expected to increase because of demographic changes.