BACKGROUND:: Anesthesiologists and certified registered nurse anesthetists (CRNAs) must acquire the skills to recognize and manage a variety of acute intraoperative emergencies. A simulation-based assessment provides a useful and efficient means to evaluate these skills. In this study, we evaluated and compared the performance of board-certified anesthesiologists and CRNAs managing a set of simulated intraoperative emergencies. METHODS:: We enrolled 26 CRNAs and 35 board-certified anesthesiologists in a prospective, randomized, single-blinded study. These 61 specialists each managed 8 of 12 randomly selected, scripted, intraoperative simulation exercises. Participants were expected to recognize and initiate appropriate therapy for intraoperative events during a 5-min period. Two primary raters scored 488 simulation exercises (61 participants × 8 encounters). RESULTS:: Anesthesiologists achieved a modestly higher mean overall score than CRNAs (66.6% ± 11.7 [range = 41.7%-86.7%] vs 59.9% ± 10.2 [range = 38.3%-80.4%] P < 0.01). There were no significant differences in performance between groups on individual encounters. The raters were consistent in their identification of key actions. The reliability of the eight-scenario assessment, with two raters for each scenario, was 0.80. CONCLUSION:: Although anesthesiologists, on average, achieved a modestly higher overall score, there was marked and similar variability in both groups. This wide range suggests that certification in either discipline may not yield uniform acumen in management of simulated intraoperative emergencies. In both groups, there were practitioners who failed to diagnose and treat simulated emergencies. If this is reflective of clinical practice, it represents a patient safety concern. Simulation-based assessment provides a tool to determine the ability of practitioners to respond appropriately to clinical emergencies. If all practitioners could effectively manage these critical events, the standard of patient care and ultimately patient safety could be improved.