It has often been argued that democracies are less war-prone than other forms of government because the people, who must bear the costs of war in lives and resources, will restrain the aggressive impulses of their leaders. Most empirical studies addressing this hypothesis have produced results indicating that democracies fight as often as other states. The authors argue that previous studies have misspecified the theoretical argument. The argument the authors propose and the test they design focus directly on specific mechanisms by which the decisions of leaders are constrained, rather than on composite conceptual and operational definitions of democracy. The authors also control for the opportunity leaders have to decide for war. Their results suggest that for major powers, higher levels of decisional constraints lead to a lower probability that conflicts will escalate to war, as the authors' theoretical argument predicts. The relationship does not hold for minor powers, however, and may even be reversed. © 1991, Sage Publications. All rights reserved.