This paper examines issues of medical professionalism using definitions and meanings as its analytic lens. It explores similarities, differences, and changes in meaning and interpretation over time and across three primary literatures of professionalism: sociology, medicine, and education. In compiling these literatures, three stages in the evolution of medical professionalism emerged: the first (1980s-early 1990s) was dominated by the polemics of professionalism and commercialism; a second (1900s) was dominated by calls to define medical professionalism as a concept and as a competency; the third (late 1990s-current) quickly superseded calls to define by highlighting the need to develop measures and metrics. Across these three stages, two sets of “authoritative voices” emerged in the medical literature with certain medical organizations and journal articles beginning to dominate, and in certain cases dictate, agendas and debates. The paper closes with an extended discussion of the largely US based and sociologically focused “new professionalism” literature, and contrasts this with a parallel UK medically based literature. The paper closes with a set of six conclusions covering the lessons learned in compiling this literature.