From the studies described in this thesis, investigating different aspects of outcome assessment in total hip arthroplasty, the following conclusions and recommendations can be made: To ensure good quality of life and adequate mobility for future elderly generations, adequate measures need to be taken to respond adequately to the increasing demand for THA, for instance with regard to future budgets for THA, the use of cost-effective prosthesis systems and training of surgeons and other medical personnel. The revision burden of THA (Total Hip Arthroplasty) in the Netherlands is relatively high compared to the Scandinavian countries. Apart from figures from a discharge registry and an implant registry with compliance less than 60% and no possibilities for follow-up, there is no registration system for THA in the Netherlands. In spite of problems with liability, compliance, cost and confidentiality with the introduction of a register, new efforts should be undertaken within the Dutch orthopaedic community to start nation-wide orthopaedic registries. Such registries should serve both as a database to study outcome after surgery and as a benchmarking tool for all participating clinics. The moderate to good compliance to existing recommendations for the indication for THA found in our survey of Dutch and Swedish orthopaedic surgeons shows the applicability of these recommendations in clinical practice. However, we found that patients in a later phase of the disease process did not improve to the level achieved by patients with a better preoperative function. Therefore, traditional orthopaedic practice, to delay surgery as long as possible, might need to be re-evaluated, especially for elderly patients. Clinical guidelines on THA, based on review of clinical evidence and involving cost-effectiveness and patient preference, should be established in both The Netherlands and Sweden. Apart from consensus statements, no such guidelines exist in either country. Because of the multiple risk factors found for re-revision for ...