The Treaty on the Non-Proliferation of Nuclear Weapons, signed on July 1, 1968, remains the bedrock of the post-World World II global nonproliferation regime. With 187 States parties, this treaty is the most widely adhered to and the most successful multilateral arms control agreement in history. Today, only four States remain non-parties: Cuba, India, Israel, and Pakistan. However, neglect, weak leadership, pressing domestic issues, post-Cold War uncertainties, and “New World Order” tensions are all hastening the erosion of the normative and organizational foundations of the nonproliferation regimes. Nonproliferation efforts face significant challenges with the situations in North Korea and Iraq. In both cases, States have violated obligations they undertook as parties to nonproliferation treaties, and in both cases, they have succeeded in delaying full compliance with the normative and legal aspects of these obligations. Another critical issue is how the nuclear weapon States, especially Russia and the United States, discuss and perceive their inventories of nuclear weapons. Also, changes in biological weapons technology and motivations may combine to make this type of weaponry a more threatening concern than nuclear weapons. Yet there is an ineffective treaty that has substantial compliance problems and to which many key States are not even party. Future nonproliferation challenges include determining the role of the United Nations and addressing the new threats that have surfaced and not been addressed by any one treaty or regime.