Since emergency medical services (EMS) programs began in the early 1970s, much has been learned about the management of out-of-hospital cardiac arrest. The key therapeutic interventions, metaphorically characterized as 4 links in a chain of survival,1 are rapid access, rapid cardiopulmonary resuscitation (CPR), rapid defibrillation, and rapid advanced life support, including endotracheal intubation, intravenous access, and medication. Many researchers propose a fifth link—timely postresuscitative care, namely, hypothermia.2 In addition, event factors such as witnessed collapse, cardiac rhythm, and comorbidity are associated with the likelihood of resuscitation. Each of these therapeutic and event factors helps explain why an individual may live or die following cardiac arrest. Yet the predictive power of each of these factors pales in comparison with one easily characterized feature. The most important, powerful, and underappreciated factor is the community in which the cardiac arrest occurs.