Introduction Advances in surgical technique, implant design, and clinical care pathways have resulted in higher expectations for improved clinical outcomes after primary THA; however, despite these advances, it is unclear whether the risk of revision THA actually has decreased with time. Understanding trends in short-and mid-term risks of revision will be helpful in directing clinical, research, and policy efforts to improve THA outcomes.Question/purposes We therefore asked (1) whether there have been changes in overall short-and mid-term risks of revision THA among patients in the Medicare population who underwent primary THA between 1998 and 2010; and (2) whether there are different demographic factors associated with short-and mid-term risks of revision THA. Methods Using the Medicare 5% national sample database, patients who underwent primary THA between 1998 and 2010 followed by subsequent revision through 2011