Objectives: To examine the responses of emergency medicine residents (EMRs) to ethical dilemmas in high-fidelity patient simulations as a means of assessing resident professionalism. Methods:This cross-sectional observational study included all EMRs at a three-year training program. Subjects were excluded if they were unable or unwilling to participate. Each resident subject participated in a simulated critical patient encounter during an Emergency Medicine Crisis Resource Management course. An ethical dilemma was introduced before the end of each simulated encounter. Resident responses to that dilemma were compared with a professional performance checklist evaluation. Multiresponse permutation procedure analysis was used to compare performance measures between resident classes, with the a priori hypothesis that mean performance should increase as experience increases. Results: Of the 30 potential subjects, 90% (27) participated. The remaining three residents were unavailable due to scheduling conflicts. It was observed that senior residents (second and third year) performed more checklist items than did first-year residents (p < 0.028 for each senior class). Omnibus comparison of mean critical actions completed across all three years was not statistically significant (p < 0.13). Residents performed a critical action with 100% uniformity across training years in only one ethical scenario (“Practicing Procedures on the Recently Dead”). Residents performed the fewest critical actions and overall checklist items for the “Patient Confidentiality” case. Conclusions: Senior residents had better overall performance than incoming interns, suggesting that professional behaviors are learned through some facet of residency training. Although limited by small sample size, the application of this performance-assessment tool showed the ability to discriminate between experienced and inexperienced EMRs with respect to a variety of aspects of professional competency. These findings suggest a need for improved resident education in areas of professionalism and ethics.