We develop a conceptual framework of political repression. To motivate why states repress, we introduce the notion of the political project. The proposed framework is used to interpret two known stylized facts: 1) repression is higher in autocracies; and 2) repression has declined since the 1990s. We discuss under-researched aspects of political repression such as migration restrictions, the targeting of repression, and backlash. We conclude by bringing attention to the two main challenges for research on repression: 1) conceptualizing whether a given episode of repression is successful, and 2) the inherent selection problem in empirical measures of repression.<br><br>Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at <a href="http://www.nber.org/papers/&#119;34926" TARGET="_blank">www.nber.org</a>.<br>