This chapter reviews the literature on deterring and preventing terrorism. Al-Qaeda committed one of the most spectacular acts of terrorism in history when it attacked four targets, including the World Trade Center towers and the Pentagon on September 11, 2001. The chapter highlights how policies and law increasing punishment might deter terrorists from attempting violent criminal acts, that other conciliatory approaches might also be effective, and that the specific statute and context play an important role. It shows that deterrence strategies might produce unintended consequence by increasing rather than reducing such behaviours. The chapter also highlights efforts to deploy situational crime prevention (SCP) strategies to respond to terrorism, discussing how understanding situational characteristics and hardening potential targets could effectively thwart terrorism without displacing it. It discusses post-9/11 intelligence efforts to overcome organizational obstacles to sharing information as well as strategies to transfer local information to the proper authorities to effectively use it to prevent terrorism.