Professionals in Emergency Medicine, Emergency Nursing, Emergency Medical Services (EMS) and other emergency healthcare disciplines have played a central role in influencing how the nation responds to emergencies and disasters, and they continue to shape this challenging area. Experts from these disciplines have been at the forefront in all aspects of healthcare emergency management, including healthcare system continuity of operations, medical surge, specialty capabilities such as managing chemical casualties, and deploying medical resources into austere environments.This chapter describes the integral roles and major influences of Emergency Medicine and emergency healthcare delivery on the past and present U.S. disaster response capabilities. These influences have occurred across all types of hazards (intentional, technological, and natural) and across all phases of comprehensive emergency management (mitigation, preparation, response, recovery). Future roles and responsibilities are also explored, including the emerging concept of Emergency Public Health as a distinct discipline, which is further described in the following chapter.