The total hip arthroplasty (THA) is an effective treatment of osteoarthritis of the hip joint. Each year, more than 16,000 THAs are performed in the Netherlands. The incidence of THA had doubled between 1980 and 1994. The medical indication has extended to younger and older patients. Due to the success of the THA the number of alternative treatments, such as arthrodesis and osteotomy decreased. The number of revision surgeries increased more than four folds, to 1,400 in 1994. Based on these data the increase of primary and revision hip arthroplasties is expected to continue, but it is unknown how much the exact increase will be. In view of the increased demand it is important to gain more insight into the numbers of primary and revision surgical procedures to be expected, so that a better estimation can be made of the health care capacity and financial resources required in the future.