During the past decade, the measurement of physician performance and offering incentives as a means of improving care have been the focus of many governmental, private, and professional groups. Performance measurement systems typically use discrete, validated clinical measures. Even though the results of these approaches have thus far been equivocal, performance measurement is already being firmly established in health care.1 The Affordable Care Act contains requirements for the Centers for Medicare & Medicaid Services to use consensus measures for payment rewards in programs such as the Physician Quality Reporting System (PQRS) and the meaningful use regulation in electronic health record use. Although hospital-based quality reporting and pay-for-performance have yielded some impressive results,1 it is uncertain whether the same will hold true in the performance of individual physicians.2 Underlying questions about individual performance include uncertainties about how to assess the influence of individual physicians in teams and systems of care and the role financial incentives should have in motivating physicians.