What are the causes and consequences of the proliferation of armed unmanned aerial vehicles, or drones? The chapter outlines several potential reasons why actors might acquire the technology: operational incentives, technological availability, regime type, and emulation before discussing the consequences of this acquisition. The consequences of drone proliferation are context dependent: drone proliferation carries potentially significant consequences for counter-terrorism operations and domestic control in authoritarian regimes. Drones lower the costs of using force by eliminating the risk to pilots, making some states—especially democracies—more likely to carry out targeted attacks against suspected militants. This technology also provides autocratic leaders with a new tool to bolster their domestic regime security. The chapter’s analysis has implications for a range of policy issues: the regulation of drone exports, the management of hotspots such as East Asia and the Middle East, and defense against potential terrorist attacks on the homeland.