Emergency department (ED) crowding and ambulance diversion has been an increasingly significant national problem for more than a decade. More than 90% of hospital ED directors reported overcrowding as a problem resulting in patients in hallways, full occupancy of ED beds, and long waits, occurring several times a week. Overcrowding has many other potential detrimental effects including diversion of ambulances, frustration for patients and ED personnel, lesser patient satisfaction, and most importantly, greater risk for poor outcomes. This article gives a basic blueprint for successfully making hospital-wide changes using principles of operational management. It briefly covers the causes, significance, and dangers of overcrowding, and then focuses primarily on specific solutions.