Domestic politics and international relations are often inextricably entangled, but existing theories (particularly “state-centric” theories) do not adequately account for these linkages. When national leaders must win ratification (formal or informal) from their constituents for an international agreement, their negotiating behavior reflects the simultaneous imperatives of both a domestic political game and an international game. Using illustrations from Western economic summitry, the Panama Canal and Versailles Treaty negotiations, IMF stabilization programs, the European Community, and many other diplomatic contexts, this article offers a theory of ratification. It addresses the role of domestic preferences and coalitions, domestic political institutions and practices, the strategies and tactics of negotiators, uncertainty, the domestic reverberation of international pressures, and the interests of the chief negotiator. This theory of “two-level games” may also be applicable to many other political phenomena, such as dependency, legislative committees, and multiparty coalitions.