The U.S. media have focused almost exclusively on the threat from containerized shipping. Most spectacular is the fear that a commercial ship could bring into the United States a weapon of mass destruction--or at least a mass casualty device such as a radiological weapon. The article finds even more frightening the danger that terrorists may use either a commercial vessel or a cruise ship as a weapon, similar to the hijacked aircraft that struck the World Trade Center and the Pentagon. The Al-Qaeda network is believed to own and operate two dozen commercial vessels. When not involved in Al-Qaeda operations, they function as any other commercial vessels, hauling cargo and generating income. The article recommends that the United States create a unified system which will oversee all aspects of its 360 ports. The system must span the military and intelligence communities and include the Coast Guard, Immigration and Naturalization Service, Customs, and other agencies as needed. Further, this is not just a question of homeland security, but of global trade and the functioning of international commerce. Washington must cooperate with its allies to create a system with which to share intelligence and encourage the international maritime industry to police itself.