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BACKGROUND To ensure validity and acceptance of NSQIP risk-adjusted benchmarking, it is important that adjustments adequately control for hospitals that vary in their proportions of lower or higher risk operations (combined risk for procedure and patient). This issue was addressed in separate empirical and simulation studies. STUDY DESIGN For the empirical study, potential miscalibration bias favoring hospitals that do lower risk operations or disfavoring hospitals that do higher risk operations was evaluated for 14 modeled outcomes using NSQIP data. A determination was also made as to whether there was a relationship between mean hospital operation risk and benchmarking results (log OR). In the simulation study of the same 14 outcomes, hospital benchmarked performance was evaluated when sampled cases were reconstituted to include either a larger proportion of lower risk operations or a larger proportion of higher risk operations. RESULTS Miscalibration favoring either lower or higher risk operations was absent, as were important associations between operative risk and hospital log ORs (most model R2 < 0.01). In the simulation, there were no substantial changes in log ORs when greater percentages of either lower or higher risk operations were included in a hospital's sample (nonsignificant P-values and effect sizes < 0.1). CONCLUSION These results should enhance NSQIP participants' confidence in the adequacy of NSQIP patient and procedure risk-adjustment methods. NSQIP participants may rely on benchmarking findings, and implement quality improvement efforts based on them, without concern that they are biased by a preponderance of lower or higher risk operations.