The European Parliament plays an increasingly important role in the process of European integration. This research project will create four connected datasets that will make feasible the first systematic empirical investigation of decisionmaking in the European Parliament. These data sets will consist of detailed bills and amendments, histories of proposed legislation, prior and subsequent actions external to the EP, and roll call floor votes. A series of case studies will focus attention of European environmental policies. Broad theoretical reasons also motivate this study. Institutional and partisan features of the EP facilitate cooperative decisionmaking which speeds integration. Understanding the ways in which these features affect decisionmaking can provide important insights into the design of institutional structures.