Misconception 1: EDs are crowded because large numbers of medically indigent patients use EDs for "primary care"Multiple factors cause emergency department (ED) crowding. The current rate of annual ED utilization in the United States is slightly above 400 visits per 1000 population, and has increased 15% during the past decade. 1 The Institute of Medicine's 2006 report "Hospital-Based Emergency Care: At the Breaking Point" cited several drivers of ED crowding including increased numbers of ED visits, a shortage of on-call specialists, and lengthy delays prior to admission ("boarding"). 2 While the ED serves as a "safety net" for the underserved, high volumes of low-acuity visits are not a major contributor to ED crowding. A recent study found that increasing diagnostic and treatment intensity was strongly associated with worsening ED crowding and that low-acuity use exerted a minimal impact. 3 In addition, multiple studies have found that prolonged times between an emergency physician's admitting decision and patient transfer from the ED to an inpatient bed ("ED boarding") is a major factor causing crowding. 4,5 Boarding has several causes, including inefficiencies resulting in slow transitions of care, inadequate inpatient capacity (bed space), and inadequate inpatient nurse staffing.Peak ED patient arrival in many hospitals occurs in the late morning through mid-evening. The decision to admit generally occurs about 2.5 hours after arrival in the ED, so inpatient bed demands from most EDs accelerate during the late morning and early afternoon. Many hospital Emergency Care and The Public's Health, First Edition. Edited by Jesse M. Pines, Jameel Abualenain, James Scott and Robert Shesser.