BACKGROUND Influenza is responsible for substantial morbidity and mortality annually. Vaccination strategies target high-risk patients. The percentage of Emergency Department (ED) patients at high risk is largely unknown. OBJECTIVE The percentage of patients at high risk for influenza was determined and compared to the United States (US) population. METHODS Medical records of a convenience sample of all patients presenting to the ED of a university-affiliated hospital in Tucson, Arizona from February 1-7, 2006 were reviewed (n = 1359). Patients were stratified as 1) at high risk for influenza or its complications, 2) health care workers (HCW), household contacts of high-risk patients, and other target populations, and (3) otherwise healthy adults. Additionally, vaccination status and prior ED utilization within that season's vaccination period was determined. RESULTS Of all patients presenting to the ED, 41.5% were at high risk for influenza or its complications (US 30.8%, p < 0.001). Of all ED patients, 10.8% were household contacts, HCWs, or in another target group (US 42.8%, p < 0.001). Of high-risk ED patients, 43.5% had been vaccinated that season (US 47.1%, p < 0.001) and 13.7% had had at least one visit to the ED within the preceding 3 months. CONCLUSIONS There is a higher percentage of patients at high risk for influenza in the ED population than the general US population. The ED may be a novel location in which to effectively identify and immunize high-risk individuals. Benefits to ED vaccination may include subsequent reductions in mortality and morbidity as well as a decrease in ED utilization and hospitalization for influenza and its complications.