This article examines the role that economic and political factors played in tax reform in Organization for Economic Cooperation and Development (OECD) countries from 1986 to 1990. Some writers argue that economic integration forced states to reform their tax systems. The authors' findings indicate that economic openness had an indirect effect on the level of change in marginal tax rates. The institutional structure of a country was most important--countries that had only one veto player or only one institution or party whose approval was necessary for a bill to become law enacted more sweeping reform than states that had more than one veto player. These results suggest that even when international or domestic economic factors might dictate a change in policy, reform will not be as sweeping in countries in which agreement among several institutions and/or parties is necessary.