Background. Surgical quality improvement has received increasing attention in recent years, yet it isn't clear where orthopaedic surgeons should focus their efforts for the greatest impact on peri-operative safety and quality. We sought to guide these efforts by prioritising orthopaedic procedures according to their relative contribution to overall morbidity, mortality, and excess length of stay. Methods. We used data from the American College of Surgeons' National Surgery Quality Improvement Program (ACS-NSQIP) to identify all patients undergoing an orthopaedic procedure between 2005 and 2007 (n=7,970). Patients were assigned to 44 unique procedure groups based on Current Procedural and Terminology codes. We first assessed the relative contribution of each procedure group to overall morbidity and mortality in the first 30 days, and followed with a description of their relative contribution to excess length of stay. Results. Ten procedures accounted for 70% of adverse events and 64% of excess hospital days. Hip fracture repair accounted for the greatest share of adverse events, followed by total knee arthroplasty, total hip arthroplasty, revision total hip arthroplasty, knee arthroscopy, laminectomy, lumbar/thoracic arthrodesis, and femur fracture repair. In contrast, no other procedure group accounted for more than 2% of morbidity and mortality. Conclusion. Only a few procedures account for the vast majority of morbidity and mortality in orthopaedic surgery. Concentrating quality improvement efforts on these procedures may be an effective way for surgeons and other stakeholders to improve peri-operative care and reduce cost in orthopaedic surgery