This USIP Special Report, written by Ethan B. Kapstein, addresses the lack of clarity on which programs best foster stability in fragile and conflict-affected areas. It is the result of a collaboration of the United States Agency for International Development (USAID), the United States Institute of Peace (USIP), and the Empirical Studies of Conflict Project at Princeton University to assess the impact of USAID’s stabilization programs on Afghanistan. The summary highlights six key conclusions of the report. Stabilization programs generally have only a modest impact on violent conflict and other key outcome measures. Policymakers and implementers should not expect to generate large or persistent effects. Smaller projects can be targeted at specific gaps in particular communities and may be less likely to fuel instability. Despite the potential benefits, the U.S. government would find it difficult—given its current management structure—to manage hundreds of smaller projects. Program design needs to account for the role of antigovernment elements. Data collection is a crucial part of program design and needs to be integrated from the outset. Evaluating the impact of complex stabilization programs in ways that can improve future programming is critical to economic development and national security. The report does not reflect the views of USIP, USAID, or any U.S. government agency.