Background: Prophylactic antibiotic (PA) administration 1 to 2 hours before surgical incision (SIP-1) is a publicly reported process measure proposed for performance pay. We performed an analysis of patients undergoing major surgical operations to determine if SIP-1 was associated with surgical site infection (SSI) rates in Department of Veterans Affairs (VA) hospitals. Study Design: Patients with External Peer Review Program Surgical Care Improvement Project (SCIP)-1 data with matched National Surgical Quality Improvement Program data were included in the study. Patient and facility level analyses comparing SCIP-1 and SSI were performed. We adjusted for clustering effects within hospitals, validated SSI risk score, and procedure type (percentage of colon, vascular, orthopaedic) using generalized estimating equations and linear modeling. Results: The study population included 9,195 elective procedures (5,981 orthopaedic, 1,966 colon, and 1,248 vascular) performed in 95 VA hospitals. Timely PA occurred in 86.4% of patients. Untimely PA was associated with a rate of SSI of 5.8%, compared with 4.6% in the timely group (odds ratio = 1.29, 95% CI 0.99, 1.67) in bivariable unadjusted analysis. Patient level risk-adjusted multivariable generalized estimating equation modeling found the SSI risk score was predictive of SSI (p < 0.001); SIP-1 was not associated with SSI. Hospital level multivariable generalized linear modeling found procedure mix (p < 0.0001), but not SIP-1 rate or facility volume, to be associated with facility SSI rate. The study had 80% power to detect a 1.75% difference for patient level SSI rates. Conclusions: Timely PA did not markedly contribute to overall patient or facility SSI rates. These data are important for the ongoing discourse on how to measure and pay for quality of surgical care. © 2008 American College of Surgeons.