This testimony begins with a brief description of the threat posed by nuclear terrorism and the current inventory of multilateral institutions relating to nuclear security. It then looks at the issue of effectiveness. Are multilateral nuclear institutions effective? A review of the first five decades of the nuclear age suggests that the nonproliferation regime has been a surprisingly powerful tool in preventing nuclear proliferation and enhancing nuclear security. The testimony then examines how these multilateral tools might fit into a broader strategy against nuclear terrorism. The underlying theme of this strategy is that homeland security begins abroad, that preventing nuclear terrorism requires that nuclear weapons and materials outside of the United States be protected from terrorists. The remarks conclude with a look at the role of Congress, and steps that might be taken to strengthen nuclear regimes and reduce the threat posed by nuclear terrorism. Three areas of Congressional action are considered: oversight, appropriations, and policy innovation.