Institutional constraints have been offered by some scholars as an explanation for why multiparty coalitions should be more peaceful than single-party cabinets. Yet others see the same institutional setting as a prescription for more aggressive behavior. Recent research has investigated these conflicting expectations, but with mixed results. We examine the theoretical bases for these alternative expectations about the effects of coalition politics on foreign policy. We find that previous research is limited theoretically by confounding institutional effects with policy positions, and empirically by analyzing only international conflict data. We address these limitations by examining cases of foreign policy behavior using the World Event ⁄ Interaction Survey (WEIS) dataset. Consistent with our observation that institutional constraints have been confounded with policy positions, we find that coalitions are neither more aggressive nor more peaceful, but do engage in more extreme foreign policy behaviors. These findings are discussed with regard to various perspectives on the role of institutions in shaping foreign policy behavior.Research on how political institutions affect foreign policy typically focuses on the pacifying consequences of democratic institutions. Political systems that include more voices and interests in the policymaking process purportedly require more time to mobilize domestic players, and input from domestic constituencies presumably constrains leaders who might otherwise take their country to war. This idea is at the heart of the institutional, or structural explanation of the democratic peace, but it has been used by others comparing different types of democratic institutions as well. Some have argued, for example, that democratic political systems with powerful legislatures, compared to systems with weak legislative bodies, will more likely render an executive reluctant to use force (Auerswald 1999;Reiter and Tillman 2002).The notion that institutional constraints translate into more peaceful international behavior has also been used in propositions regarding the effects of coalition politics on the foreign policy of multiparty cabinets. Yet an alternative