Background: It has been shown that medical student professionalism is influenced by the hidden curriculum, although the extent to which this occurs during the surgery clerkship is unknown. Furthermore, the processes within the hidden curriculum have been used to teach professionalism to medical students, but this strategy has not been used during the surgery clerkship. The purpose of this study was to review a 2-year experience with a surgery clerkship instructional session where the hidden curriculum was used to teach professionalism to medical students. Study Design: Medical student essays were analyzed to evaluate the influence of the hidden curriculum on their ideas about professionalism and to identify specific behaviors that they regarded as professional and unprofessional. The instructional session was evaluated using the average satisfaction session ratings and through an analysis of medical student session evaluation comments. Results: Seventy-five percent of medical students reported that their ideas about professionalism changed. This change involved their general concepts about professionalism, identifying specific behaviors that they planned to adopt or avoid, or developing opinions about the professionalism of surgeons. The average satisfaction rating was consistently high throughout the study period, and the most helpful session feature was reported as the opportunity to share and discuss their observations. Conclusions: The hidden curriculum has a substantial influence on the development of professionalism of medical students during the surgery clerkship. It was possible to illuminate and use the hidden curriculum to create an instructional session devoted to professionalism for medical students on the surgery clerkship. © 2012 Association of Program Directors in Surgery.