Whether U.S. terrorism-prevention efforts match the threat continues to be central in policy debate. Part of this debate is whether the United States needs a dedicated domestic counterterrorism intelligence agency. To inform future policy decisionmaking, this book examines, from a variety of perspectives, the policy proposal that such an agency be created. These include its possible capabilities, comparing its potential effectiveness with that of current efforts, and its acceptability to the public, as well as various balances and trade-offs involved in creating such an agency. Reflecting the limits in the data available and the significant uncertainty associated with this policy area, if there is a unifying message from the study, it is one of caution and deliberation. In an area in which direct assessment and analysis are limited, there is a need to carefully consider the implications and potential outcomes of such significant policy changes. In doing so, examination from different perspectives and through different approaches -- to ideally capture a sufficient picture of the complexity to see not just the benefits we hope to gain from policy change but the layers of effects and interactions that could either help or hurt the chances of those benefits appearing -- is a critical ingredient of policy deliberation and design.