Several reports have documented the prevalence and severity of emergency department (ED) overcrowding at specific hospitals or cities in Canada; however, no study has examined the issue at a national level. A 54-item, self-administered, postal and web-based questionnaire was distributed to 243 ED directors in Canada to collect data on the frequency, impact and factors associated with ED overcrowding. The survey was completed by 158 (65% response rate) ED directors, 62% of whom reported overcrowding as a major or severe problem during the past year. Directors attributed overcrowding to a variety of issues including a lack of admitting beds (85%), lack of acute care beds (74%) and the increased length of stay of admitted patients in the ED (63%). They perceived ED overcrowding to have a major impact on increasing stress among nurses (82%), ED wait times (79%) and the boarding of admitted patients in the ED while waiting for beds (67%). Overcrowding is not limited to large urban centres; nor is it limited to academic and teaching hospitals. The perspective of ED directors reinforces the need for further examination of effective policies and interventions to reduce ED overcrowding.