The flourishing role of the private sector in security management over the last twenty years has challenged state control of the legitimate use of force. Deborah Avant examines the privatization of security and its impact on the control of force. She describes the growth of private security companies, explains how the industry works, and describes its range of customers—including states, non-government organizations and commercial transnational corporations. Avant also charts the inevitable trade-offs that the market for force imposes on the states, firms and people wishing to control it, and suggests a new way to think about the control of force.