The use of arterial tourniquets in prehospital emergency care has been fraught with controversy and superstition for many years despite the potential utility of these tools. This review examines this controversy in the context of the history of the tourniquet as well as its recent use in surgery and modern battlefield casualty care. Safe prehospital tourniquet use is widespread in the military and is based on sound physiologic data and clinical experience from the surgical use of tourniquets. The physiologic, pathophysiologic, and clinical underpinnings of safe tourniquet use are reviewed here, along with a discussion of alternatives to tourniquets. Prehospital settings in which tourniquets are useful include tactical emergency medical services (EMS) and other law enforcement environments as well as disaster and mass casualty incidents. Beyond this, we present arguments for tourniquet use in more routine EMS settings, in which it may be beneficial but has heretofore been considered inappropriate. Protocols that foster safe, effective prehospital tourniquet use in these settings are then presented. Finally, we discuss future directions in which tourniquet research and other initiatives will further enhance the safe, rational use of this potentially life-saving tool.