Abstract : The possible proliferation of chemical, biological, and nuclear weapons (known collectively as Weapons of Mass Destruction-WMD) and their delivery systems to additional nations or subnational groups poses significant challenges for U.S. national security policy. The complex challenges presented by the threat of WMD proliferation have diplomatic, technological, and economic aspects. The United States is a signatory to several international agreements, including the Nuclear Nonproliferation Treaty, the Chemical Weapons Convention, and the Biological Weapons Convention, that seek to contain the spread of these weapons to other nations. Washington also pursues policies that seek to slow or prevent the proliferation of weapons or materials from specific countries, such as Russia, Pakistan, and China, and to dissuade or prevent the acquisition of these weapons and related technologies by specific countries, such as Iran and North Korea, and subnational or terrorist groups. In its second session, the 111th Congress is expected to continue its oversight of the full range of programs that address WMD proliferation challenges. For example, the United States provides approximately $1 billion annually in assistance to Russia and other former states of the Soviet Union to help them secure WMD sites and to prevent the export of WMD technical expertise. Under the Proliferation Security Initiative, the United States and more than 90 countries have agreed to strengthen efforts to interdict shipments of WMD or related cargo. The Department of Energy's Global Threat Reduction Initiative (GTRI) works to secure and remove nuclear and radiological materials worldwide. Congress may renew its deliberation over the funding for these efforts, the amounts allocated to specific projects and programs, and whether additional funding should be provided to allow expansion of these programs to other countries of concern.