Large-scale natural, human-made, or terrorism-related incidents rarely lend themselves to management via the standard day-to-day operational bureaucracy of the affected agencies, jurisdictions, and organizations. Incident command systems (ICS) and the National Incident Management System provide a standardized framework that allows the portability, flexibility, scalability, and interoperability required to effectively manage the wide variety of emergency incidents. This chapter will discuss the basic tenets of ICS, including the overall structure of and specific positions within a command organization under ICS; the importance of standardization of roles and terminology; the importance of planning, communication, and interoperability in the response to a major incident; and the concept of scalability, allowing ICS to be used in responses to events of varying magnitude. A basic understanding of the role and framework of a standardized incident management system will better prepare EMS physicians to operate within such a system in response to any emergency incident.