Those who educate medical students and physicians work in a world suffused with the concept of competency. This article examines the intellectual origins and hidden assumptions of this concept and argues that it is an inadequate, and even harmful, concept to use as a guiding motif for professional education. The competency model-which tends to be top-down and prescriptive-does not provide the framework for objective educational assessment that it claims to provide. The alternative apprenticeship model is more appropriate for professional education and is more consistent with what psychological research has shown about the acquisition of expertise.