This study is part of a larger effort at the NDU Center for Counterproliferation Research to identify regional strategies that contribute to enhanced deterrence of employment of nuclear, biological, and chemical (NBC) weapons and their means of delivery. This particular assessment of Iran and the challenges of deterring its use of NBC weapons was the annex to a broader evaluation of regional deterrence, which includes Iran and North Korea as case studies. Both the broader deterrence paper and the North Korean case study will be published separately. While much unclassified literature is available on both deterrence theory and Iran, the present study was facilitated by the fairly narrow scope of the questions being asked about Iran: what makes Iran easier or harder to deter, and what can the United States do to enhance our ability to deter Iran's use of NBC weapons? The Islamic Republic of Iran presents a particular challenge to the Western analyst: Iranian leaders do not see the world from the Western view and have demonstrated a willingness to undertake actions at times seemingly contrary to their national interests and at a cost other states would find unacceptable. This does not make them irrational or necessarily undeterrable. The factors that influence their cost/benefit calculations, however, may be very different than those that have guided Western concepts of deterrence over the past 50 years. Thus it was important throughout the research to make every effort to avoid imposing Western perspectives and values on the evidence. Conclusions based on superimposed but inaccurate perspectives are often wrong and, in light of the need to deter Iranian NBC use, could be dangerously wrong in the not-distant future.