The evolution of the emergency medical services system in the United States accelerated rapidly between 1960 and 1973 as a result of a number of medical, historical, and social forces. Current emergency medical services researchers, policy advocates, and administrators must acknowledge these forces and their limitations and work to modify the system into one that provides uniformly high-quality acute care to all patients, improves the overall public health through injury control and disease prevention programs, participates as a full partner in disease surveillance, and is prepared to address new community needs of all types.