Three central goals motivate this introductory essay and the articles that follow. First, we seek better understanding of the EU's own institutions, especially to the extent that they play a role in or represent the process of integration. Second, we seek better integration of the multiple general understandings of institutions and primarily of rationalist and constructivist conceptions. Third and most important, we seek to promote the integration of institutional research. Our overarching argument is that metatheoretical debate about institutions has run its course and must now give way to theoretical, methodological, and carefully structured empirical dialogue. To this end, we offer specific strategies for promoting greater synthesis among competing institutional schools.