Providing public security is a fundamental function of government. As the class and degree of threat vary, government agencies must adapt to changing conditions or risk failing their basic mission. The events of September 11, 2001, illustrated the limits of governmental performance in identifying and interrupting actions intended to harm innocent citizens. These events are examined against the resources, range, and limits of governmental capacity to adapt to the emerging threat of terrorism, and an alternative perspective on administrative performance as a complex adaptive system is proposed. This perspective redefines the search for public security as a dynamic process that balances mechanisms of control with processes of information search, exchange, and feedback among public, private, and nonprofit organizations and is supported by a well–designed information infrastructure. The article concludes that the search for public security is an interactive learning process that, while guided by public organizations, must involve responsible participation by private and nonprofit organizations as well as an informed citizenry.