In political science, one issue still in need of greater theorizing is the proper measurement of bureaucratic autonomy, that is, the degree of discretion that political principals should grant to bureaucratic agents. This article reviews the literature on bureaucratic autonomy both in US administrative law and in political science. It uses the American experience to define five mechanisms by which political principals grant and limit autonomy, then goes on to survey the comparative literature on other democratic systems using the American framework as a baseline. Other democracies use different mixtures of these mechanisms, for example by substituting stronger ex post review for ex ante procedures or using appointment and removal power in place of either. We find that the administrative law and social science literatures on this topic approach it very differently, and that each would profit from greater awareness of the other discipline.