Multicenter clinical trials (MCT) have an important role in the assessment of total joint arthroplasty. The primary reason for such MCT is the need to have access to a large number of patients. In Sweden, failure after total hip arthroplasty has been recorded prospectively since 1979. Medical records from every reoperation are documented and computer analyzed. This MCT has shown that patient-related, surgical, and implant-related parameters are of importance to rates of failure. There were an increasing number of revisions after total hip arthroplasty in Sweden between 1979 and 1986. Male gender and young age increase the risk of revision. The primary diagnosis is very important for type of failure. The risk of deep infection is small but increases with the number of previous operations. Aseptic loosening has emerged as the main problem and is the cause for 74% of all revisions. Prosthetic design is of utmost importance for the rate of failure, and significant differences exist among different prosthesis types with respect to long-term survival. Finally, this MCT has shown that revisions for total hip arthroplasty in patients younger than 70 years of age eventually have failed in Sweden whenever the cemented technique has been used.