“…1,2 The phenomenon of ED overcrowding cannot be attributed to any single factor 1 but instead appears to be a product of complex causal relations, encompassing several internal and external factors, 1,3,4 most of which are beyond the control of ED staff. 4 Possible causes include use of the ED for non-emergent cases, 5,6 an aging population, 1 increasing patient acuity, 4 labour shortages, 1,4 lack of community-based alternatives to the ED, 1 delays while waiting for laboratory testing to be completed, 4 lack of public education regarding appropriate ED use and the range of services available in general practitioners' offices, 1,7 lack of long-term care and other alternative settings, 1 and lack of availability of ED or inpatient beds (or both). 1,2,4,[8][9][10][11][12] In contrast to previous studies, which have investigated overcrowding issues within the context of a single ED [1][2][3][4]9,11,12 or addressed specific causes of the problem 8,9,11,[13][14][15] (Predy G, Fraser-Lee N, Gardener K, Edwards J, Brown J, Truman C. Emergency room use for nonurgent medical conditions and the "after hours" accessibility of family physicians in the Capital Health Authority region; unpublished manuscript) we took a systems-based approach, using data from multiple sites within an integrated geographic health region.…”