Israel would regard any expansion of nuclear weapons capability within its region as an intolerable threat to its survival. As such, Iran's developing nuclear program has triggered serious concern in Israel and speculation that the Israeli government may choose to attack Iran's nuclear installations in an effort to delay its acquisition of nuclear weapons capability. This Center for Preventive Action Contingency Planning Memorandum by Steven Simon assesses the likelihood of an Israeli strike on Iran, the policy options available to diminish that likelihood, the implications should it take place, and measures that can be taken to mitigate the consequences should it occur. The memo concludes that Israel is not eager to start a war with Iran, or disrupt its relations with the United States, but it will act if it perceives an imminent existential threat in the form of a nuclear Iran. Thus, American arguments for restraint must be backed by concrete measures to contain the perceived threat and affirmations of the special relationship.