Introduction: The Implant Retrieval Laboratory at Orthopaedic Hospital has been collecting and studying retrieved metal-on-metal total hip replacements for over 15 years. The analysis of these implants has provided important insights into their clinical wear performance and the biocompatibility of the wear products. In addition to stem-type implants of first generation (McKee-Farrar) and modern generation (Metasul) implants with metal-on-metal bearings, the lab has performed analysis on over 200 failed metal-on-metal hip resurfacing devices to determine factors relevant to their failure. The primary goal of these analyses was to understand the failure mechanisms and the ways in which failures may be preventable through optimized patient selection and surgical techniques. Lessons learned from these implants include: well-manufactured and well-placed metal-onmetal implants have very low wear rates; conversely poorly manufactured or badly placed implants can have high wear rates; hip resurfacing failures are most often the result of bad bone quality, bad surgical technique or both. Perhaps the most significant finding is that despite the presence of an implant producing wear debris and altering biomechanical stresses, the majority of hip joints heal, adapt and provide a clinically successful outcome.