The essays in this volume draw on an analysis of over 80 attempts at democratic regime change, some successful, others not, in what Samuel Huntington termed the "Third Wave" of democratization. Why do some authoritarian regimes collapse in the face of pressures to democratize, while others survive? And what does this tell us, in turn, about the factors thought to promote democracy? The essays in this volume draw on a comprehensive analysis of over 80 attempts at democratic regime change, some successful, others not, in what Samuel Huntington memorably termed the "Third Wave" of democratization, beginning with Portugal's Carnation Revolution in 1974. The focus is on factors-internal, external, and contextual-that can promote democratic regime change, and under what conditions they are effective or ineffective. Legacies of the past, civil society, and elite dynamics are among the internal factors under examination, along with economic development and crises, and the role of "stateness," especially when it is weak. On the external front, chapters address both structural (long-term) and conjunctural (short-term) factors, with particular attention to the varying impacts of interventions by international actors, whether specifically intended to promote democracy or not. Geography (political, economic, human, and cultural), which helps delimit and condition the process of political change, also receives attention. While some scholars argue that we have now experienced a fourth or even a fifth wave of democratization, the roughly 40 years following the Portuguese revolution featured an incomparably large and diverse set of efforts to democratize. The lessons to be drawn from that huge body of data remain highly relevant as we seek to understand the outcomes of more recent "color revolutions" or the Arab Spring, and as we consider the future of democratization.