Professionalism, which is a core competency for physicians, can be described as a spectrum of behaviors and may have a significant impact on the problems in today's changing health care climate. In this article, we discuss the meaning of professionalism and its role in the Southern California Permanente Medical Group (SCPMG) and consider how it may be applied to integrated care delivery systems such as Kaiser Permanente. To understand professionalism, one must consider Stern's definition, which consists of four principles: excellence, humanism, accountability, and altruism. SCPMG has taken three of these principles-excellence, accountability, and altruism-and divided the fourth, humanism, into another three principles similar to those identified by the University of California Los Angeles Task Force on Professionalism: humanitarianism, respect for others, and honor and integrity. SCPMG has a rich history and culture of promoting clinical excellence and professionalism, as evidenced by the programs and initiatives described throughout this article. Indeed, the SCPMG experience validates professionalism as a core physician competency comprising a set of behaviors that are continually refined.