Nuclear nonproliferation efforts traditionally have focused on controlling the supply of proliferation-relevant technology, material, and expertise. As barriers to diffusion of all three have been lowered, there is increased acknowledgement of the need to reduce demand for such weapons, and, in cases where efforts to prevent proliferation have failed, the need to develop effective international responses. However, with few exceptions, approaches to nonproliferation have remained qualitatively the same over the last sixty years. In addition, many states whose active support is essential, view nonproliferation as primarily a U.S. issue and in some cases see U.S. military superiority as a more serious threat to their security than nuclear proliferation. Such states are often unresponsive to requests to strengthen their nonproliferation efforts. In this paper we develop a basic systems dynamics model of the process of proliferation against which nonproliferation strategies can be assessed. This basic model includes both processes of acquisition of nuclear weapons and processes that motivate states to seek nuclear weapons. Next we develop simple models of nonproliferation strategies and demonstrate how they impact the process of proliferation. We then offer observations about the relative impact of different strategies, given hypothetical initial and boundary conditions. Finally, we recommend additional work to improve the model and make it accessible to the nonproliferation community both for discussion and for testing hypotheses. Introduction Nuclear nonproliferation efforts have evolved over time in response to a changing international environment. International Atomic Energy Agency (IAEA) safeguards coupled with diplomacy were the prevailing nonproliferation strategies until the Indian nuclear test in 1974, which triggered much more intensive efforts on international export control and the formation of the Nuclear Suppliers Group. The end of the Soviet Union in 1991 and fears of unsecured nuclear weapons and material resulted in creation of a broad range of cooperative threat reduction efforts to improve nuclear security; in the same time frame, the failure of the IAEA to detect the Iraqi nuclear program led to the IAEA Additional Protocol. Since 9/11 many new approaches have been tried, ranging from capacity building to help developing countries implement nonproliferation obligations, to the Proliferation Security Initiative aimed at interdicting illicit shipments. There have also been calls for internationalization of portions of the nuclear fuel cycle and for reducing the salience (and numbers) of nuclear weapons. * Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.