Objectives To characterize emergency department (ED) use by nursing home residents in the United States. Design Analysis of the National Hospital Ambulatory Medical Care Survey. Setting U.S. EDs from 2005 to 2008. Participants Individuals visiting U.S. EDs stratified according to nursing home residency. Measurements All ED visits by nursing home residents were identified. The demographic and clinical characteristics and ED resource utilization, length of stay, and outcomes of nursing home residents and nonresidents were compared. Results During 2005 to 2008, nursing home residents accounted for 9,104,735 of 475,077,828 U.S. ED visits (1.9%; 95% confidence interval (CI) = 1.8-2.1%). The annualized number of ED visits by nursing home residents was 2,276,184. Most nursing home residents were older (mean age 76.7, 95% CI = 75.8-77.5), female (63.3%), and non-Hispanic white (74.8%). Nursing home residents were more likely to have been discharged from the hospital in the prior 7 days (adjusted odds ratio (aOR = 1.4, 95% CI = 1.1-1.9), to present with fever (aOR = 1.9, 95% CI = 1.5-2.4) or hypotension (systolic blood pressure ≤90 mmHg, aOR = 1.8, 95% CI = 1.5-2.2), and to receive diagnostic tests (OR = 1.9, 95% CI = 1.6-2.2), imaging (OR = 1.5, 95% CI = 1.3-1.7), or procedures (OR = 1.6, 95% CI = 1.4-1.7) in the ED. Almost half of nursing home residents visiting the ED were admitted to the hospital. Nursing home residents were more likely to be admitted to the hospital (aOR = 1.8, 95% CI = 1.6-2.0) and to die (aOR = 2.3, 95% CI = 1.6-3.3). Conclusion Nursing home residents account for more than 2.2 million ED visits annually in the United States. Nursing home residents have greater medical acuity and complexity. These observations highlight the national challenges of organizing and delivering ED care to nursing home residents in the United States. © 2011, The American Geriatrics Society.