The September 11, 2001 attacks brought to the forefront long-standing concerns that terrorists could severely disrupt the global supply chain by using shipping containers or vessels to attack population centers or critical infrastructure. The U.S. and multilateral regulators responded by implementing security requirements that focus on the maritime industry. It is difficult to quantify the economic impacts of these regulations as maritime shipping firms have been either reluctant to share their data for proprietary and security reasons or have not been able to quantify costs. This article reports on how firms involved in U.S. waterborne container trade have responded to the new maritime container security initiatives. Senior container line executives, port officials, and marine terminal security officers were interviewed. It is concluded that the biggest benefit of the new security requirements is that they have fostered a cooperative security relationship between industry and government. There remain, however, important issues such as port security funding and supply chain recovery that need to be addressed more fully.