The Modular Emergency Medical System (MEMS) offers a comprehensive plan of operations and standards for responding to a mass casualty event of such size that alternate care delivery sites would be required. MEMS emerged in response to Title IV of The Defense against Weapons of Mass Destruction Act of 1996 (Public Law 104-201). The law required that the Secretary of Defense develop and carry out a program to improve the responses of Federal, State, and local agencies to emergencies involving biological and chemical weapons. In response, the U.S. Department of Defense (DOD) created the Biological Warfare Improved Response Program. DOD then invited the Departments of Health and Human Services (DHHS), Energy (DOE), and Agriculture (USDA), and the Federal Emergency Management Agency (FEMA), the Federal Bureau of Investigation (FBI) and the Environmental Protection Agency (EPA), as well as emergency responders and managers from multiple States and local communities, to participate. MEMS offers detailed standards for a system of care that can be expanded and contracted in modular units as the need arises. It provides a framework for the organization of care, particularly for setting up predetermined, special-use alternate care sites. Thus, MEMS answers the questions of what general kinds of care are provided and where (alternate site standards). In specifying the staffing required for alternate care sites, MEMS also addresses who will provide care. One of the underlying assumptions in MEMS is that resources will be brought in or created within the area most affected by the mass casualty event. (AHRQ, Altered Standards of Care in Mass Casualty Events, 2005, p. B-2)