In Norway a national register for total hip replacements was established in September 1987. Up till February 1991, 17,444 total hip replacements (THR) were reported, i.e., 140 THR/100,000 inhabitants/year. The median age of the patients was 70 years, and 69 percent were women. 87 percent were primary arthroplasties and 13 percent were revisions. Primary arthrosis was the diagnosis in 68 percent of the primary operations. The acetabular implants were uncemented in 17 percent and the femoral implants in 12 percent of primary operations. In revisions, the implants were uncemented in 21 and 17 percent, respectively. The reasons for revision were loosening of components in 87 percent and deep infection in 4 percent. The Charnley prosthesis dominated with 49 percent of all implants. A total of 422 different designs and sizes of acetabular implants, 398 femoral implants and 166 of caput designs and sizes were used. This large number of different types and designs seems unreasonable.