Background: Few studies have evaluated the effect of Emergency Department (ED) overcrowding on resident education. Objectives: To determine the impact of ED overcrowding on Emergency Medicine (EM) resident education. Materials and Methods: A prospective cross-sectional study was performed from March to May 2009. Second- and third-year EM residents, blinded to the research objective, completed a questionnaire at the end of each shift. Residents were asked to evaluate the educational quality of each shift using a 10-point Likert scale. Number of patients seen and procedures completed were recorded. Responses were divided into ED overcrowding (group 0) and non-ED overcrowding (group N) groups. ED overcrowding was defined as >2 h of ambulance diversion per shift. Questionnaire responses were compared using Mann Whitney U tests. Number of patients and procedures were compared using unpaired T-tests. Results: During the study period, 125 questionnaires were completed; 54 in group 0 and 71 in group N. For group 0, the median educational value score was 8 (interquartile range [IQR] 7-10), compared to 8 (IQR 8-10) for group N (p = 0.24). Mean number of patients seen in group 0 was 12.3 (95% confidence interval [CI] 11.4-13.2), compared to 13.9 (95% CI 12.7-15) in group N (p = 0.034). In group 0, mean number of procedures was 0.9 (95% CI 0.6-1.2), compared to 1.3 (95% CI 1-1.6) in group N (p = 0.047). Conclusions: During overcrowding, EM residents saw fewer patients and performed fewer procedures. However, there was no significant difference in resident perception of educational value during times of overcrowding vs. non-overcrowding. (C) 2012 Elsevier Inc.