Triage is an essential function in Emergency Departments (EDs), where many patients may present simultaneously. It aims to ensure that patients are treated in the order of their clinical urgency which refers to the need for time-critical intervention. Clinical urgency is not synonymous with complexity or severity. Triage also allows for the allocation of the patient to the most appropriate assessment and treatment area, and contributes information that helps to describe the departmental case-mix. Changing models of care in some EDs (for example streaming, clinical initiatives nurses, triage liaison physicians) do not preclude the need for triage.