Health care delivery systems are widely studying and implementing physician pay for performance (P4P) initiatives to improve quality and control costs. However, the increasing focus on quality-driven financial incentives has some troubling implications for medical professionalism. This article examines the P4P concept in light of a notion of medical fiduciary professionalism that dates back to the 18th-century Scottish physician John Gregory. Gregory's principles serve as a framework to assess the appropriateness of P4P initiatives in disseminating the principles of high-quality care without damage to professionalism, the patient-physician relationship, and access to care for all patients.