Canadian hospitals gather few emergency department (ED) data, and most cannot track their case mix, care processes, utilization or outcomes. A standard national ED data set would enhance clinical care, quality improvement and research at a local, regional and national level. The Canadian Association of Emergency Physicians, the National Emergency Nurses Affiliation and l'Association des médecins d'urgence du Québec established a joint working group whose objective was to develop a standard national ED data set that meets the information needs of Canadian EDs. The working group reviewed data elements derived from Australia's Victorian Emergency Minimum Dataset, the US Data Elements for Emergency Department Systems document, the Ontario Hospital Emergency Department Working Group data set and the Canadian Institute for Health Information's National Ambulatory Care Reporting System data set. By consensus, the group defined each element as mandatory, preferred or optional, and modified data definitions to increase their relevance to the ED context. The working group identified 69 mandatory elements, 5 preferred elements and 29 optional elements representing demographic, process, clinical and utilization measures. The Canadian Emergency Department Information System data set is a feasible, relevant ED data set developed by emergency physicians and nurses and tailored to the needs of Canadian EDs. If widely adopted, it represents an important step toward a national ED information system that will enable regional, provincial and national comparisons and enhance clinical care, quality improvement and research applications in both rural and urban settings.