Across the United States, emergency departments (EDs) are plagued by overcrowding and its deleterious effects. Consequently, investigators have attempted to identify a subset of nonurgent patients who could potentially be managed in alternative settings to help alleviate the burden of overcrowding. Previous authors have used several methods to define ED visit urgency; however, the lack of a single valid method has resulted in widely variable estimates of nonurgent ED use. Accurate identification of nonurgent ED visits is necessary to compare nonurgent populations across health care settings and design safe, effective interventions aimed at reducing ED overcrowding. In this paper, we review the currently used methods for the classification of ED visit urgency, discuss the implications of measurement of ED urgency for health care stakeholders, and suggest future directions for the feasible, practical measurement of ED urgency.