Background Female patients undergoing hip resurfacing arthroplasties may be at greater risk of revision surgery than males, but it is unclear whether this is related to sex or other factors. We focused our analysis on data from a prospective multicenter cohort study monitoring the ASR TM hip resurfacing arthroplasty prosthesis on the potential association of sex on patient-reported outcome measures (PROMs), metal ion levels, revision surgery, and presence of adverse local tissue reaction. As thousands of patients with the ASR TM prosthesis are still undergoing followup it is critical to optimize the protocol for monitoring these patients.Questions/purposes We wished (1) to assess the associations between sex and implant survival, and adverse local tissue reaction; and (2) to report the differences between sexes in metal ion levels and patient-reported outcome measures. Methods One thousand two hundred fifty-two patients (1390 hips) who underwent hip resurfacing arthroplasty with implantation of the ASR TM prosthesis from April 2003 to July 2010 were eligible for enrollment in a multicenter followup study of the ASR TM Hip Resurfacing System after the voluntary recall of this device was initiated by DePuy in 2010. Nine hundred seventy patients (1098 hips) were enrolled at a mean of 7 years after surgery, with a mean followup of 2 years (range, 1-3.5 years). One of the authors (OM), or a member of his immediate family, has or may receive payments or benefits, during the study period, an amount of USD 10,000 to USD 100,000, from Zimmer Inc, Biomet, Corin (Cirencester, UK), Iconacy (Warsaw, IN, USA), Renovis (Redlands, CA, USA), Conformis (Burlington, MA, USA), Aston Medical (Saint-É tienne, France), Meril Healthcare (Vapi, Gujarat, India), Arthex (Naples, FL, USA), Mako Surgical Corp, Cambridge Polymer Group (Boston, MA, USA), and Orthopedic Technology Group (Boston, MA, USA). One of the authors (HM), or a member of his immediate family, has or may receive payments or benefits, during the study period, an amount of USD 10,000 to USD 100,000, from Zimmer Inc, Biomet, Corin, and RSA Biomedical (Umeå, Sweden Nine hundred fifty-eight patients (1084 hips) met the inclusion criteria: ability to provide informed consent, complete PROMs, and continued routine followup. A subset of patients (150 patients, 171 hips), who all were from one center, with annual metal artifact reduction sequence MRI were analyzed. Ninety-three percent of patients from this center had routine MRI performed. The EuroQoL (EQ-5D), Harris hip score (HHS), University of California Los Angeles (UCLA) activity score, VAS pain, radiographs, patient and surgery details, and blood cobalt and chromium levels were obtained. Cox regression analysis was conducted to identify factors associated with implant survival, using any revision as the end point, and presence of adverse local tissue reaction. Results In patients who had unilateral surgery, the only variable found to be associated with revision surgery was HHS (hazard ratio [HR], 0.96; 95% CI, 0.9...