OBJECTIVES: Surgical site infection (SSI) occurs in approximately 2% of patients undergoing surgery, with outcomes ranging from mild to life threatening. Staphylococcus aureus is a virulent pathogen frequently identified as a cause of SSI. Cost-utility analyses are useful for assessing and comparing the value of treatments developed to address and reduce the risk of these infections. Therefore, the purpose of this study was to estimate utilities associated with varying levels of post-surgical Staphylococcus aureusinfection following joint (hip or knee) and spine surgery. METHODS: In time trade-off (TTO) interviews with a 1-year time horizon, general population participants in the UK (London, Edinburgh) valued health states drafted based on literature and clinician interviews. The health states described a year including either joint or spine surgery, with or without post-surgical infection. For joint surgery health states, possible infections included superficial wound infection, deep infection requiring debridement and implant retention (DAIR), and deep infection requiring two-stage revision arthroplasty. Spine surgery health states described infections either requiring or not requiring surgical intervention. RESULTS: A total of 201 participants completed interviews (50.25% female; mean age=46.2y). The mean (SD) utilities of health states describing a year with joint and spine surgery without infections were 0.79 (0.23) and 0.78 (0.23), respectively. Disutilities (i.e., utility decrease) of infections associated with joint surgery were -0.03 (superficial), -0.18 (DAIR), and -0.32 (two-stage revision arthroplasty). Disutilities of infections associated with spine surgery were -0.03 (infection not requiring surgery) and -0.16 (infection requiring surgery). T-tests comparing health states without infection to those with infections found that these disutilities were statistically significant (all p<0.001). CONCLUSIONS: Findings suggest that the vignette-based TTO method was feasible for quantifying the disutility of post-surgical infection. It may be useful to incorporate these disutilities into cost-utility models comparing among interventions intended to reduce the risk of post-surgical infections.