Over the past 25 years, the United States has made support for the spread of democracy to other nations an increasingly important element of its national security policy. These efforts have created a growing demand to find the most effective means to assist in building and strengthening democratic governance under varied conditions. Since 1990, the U.S. Agency for International Development (USAID) has supported democracy and governance (DG) programs in approximately 120 countries and territories, spending an estimated total of $8.47 billion (in constant 2000 U.S. dollars) between 1990 and 2005. Despite these substantial expenditures, our understanding of the actual impacts of USAID DG assistance on progress toward democracy remains limited—and is the subject of much current debate in the policy and scholarly communities. This book, by the National Research Council, provides a roadmap to enable USAID and its partners to assess what works and what does not, both retrospectively and in the future through improved monitoring and evaluation methods and rebuilding USAID's internal capacity to build, absorb, and act on improved knowledge.