Total hip arthroplasty (THA) is consistently being identified as the most successful procedure in orthopedics with excellent long-term results in terms of implant survival and improvement in quality of life. National arthroplasty registries have made an important contribution to the development and quality improvement of care for patients undergoing THA. Initially, national joint registries were primarily used as a safety instrument with a post-market surveillance function ensuring long-term device follow up. As data collection expanded, the function and aim gradually evolved from merely device registration and monitoring safety, to quality registries, with an important scientific function, linking outcome of arthroplasty to not only the prosthesis, but also to patient and surgically related factors. Furthermore, since registries have been expanded by the registration of Patient Reported Outcome Measures (PROMs), outcome of joint arthroplasty can be evaluated in terms of functional results and health-related quality of life. In this thesis a number of contemporary issues affecting outcome for patients undergoing primary THA are discussed. The general aim is to assess factors associated with survival of the prostheses and PROMs after primary THA in the Netherlands based on national register data. This thesis is divided into three parts according to three major determinants of outcome following THA: (1) the patient, (2) the orthopedic surgeon and (3) the prosthesis. In the first part of this thesis we determined the effect of patient characteristics on outcome of primary THA. The second part focused on factors predominantly determined by the orthopedic surgeon. The third part focussed on the prosthesis.