This book examines the usefulness of economic sanctions in the prevention of the proliferation of Weapons of Mass Destruction (WMD). Focusing on nuclear proliferation and utilizing the existing sanctions literature, this book examines three cases where sanctions played a role in U.S. policy. The cases are South Africa, Libya and Iraq, and the thesis' findings demonstrate that sanctions are a useful nonproliferation tool. Further, this book delivers several insights into what factors ensure policy success when using economic coercion to convince countries to give up their WMD. Security assurances, for example, can be useful in using sanctions as a nonproliferation tool. By contrast, threats of regime change can create disincentives for leadership to alter WMD-acquisition strategies. This is especially true when the U.S. Congress adds other conditions to WMD-specific sanctions. Inconsistencies in U.S. nonproliferation policy can also motivate states to acquire WMD, if countries believe Washington has turned a blind eye to an enemy's WMD programs. This book takes these insights forward to examine the evolving sanctions regime against Iran's nuclear program. It concludes that, without cautious adjustment to U.S. policy, these sanctions are likely to fail.