DescriptionThis thesis contributes to the literature on everyday policy-making in the European Union by providing insights into the determinants of member state preferences on environmental issues that are negotiated in the Council of the European Union. By presenting the first large-scale quantitative study of a whole sector, it acknowledges the sector-specificity of European political competition and helps in developing a more sophisticated understanding of policy-making in the European Union. I isolate 76 issues in legislative proposals that deal with environmental regulation from the DEUII dataset and use the member state preferences contained in it to test a theoretical framework made up of three theories of European integration and political contestation. I apply Liberal Intergovernmentalism, Neofunctionalism as well as the Constructivist argument that ideas matter to member state preference formation in everyday environmental policy-making and only find support for Liberal Intergovernmentalism. Random-effects generalized least squares regression as well as random-effects ordered logistic regression reveal that only Liberal Intergovernmentalism in its regulatory formulation is supported, while the expectations of Neofunctionalism and Constructivism are not confirmed. In substantive terms, this means that countries with lower levels of development and therefore lower environmental standards show stronger opposition towards European environmental regulation when the affected economic sector is important for the national economy, but stronger support when they have high levels of development and therefore higher environmental standards, ceteris paribus. Thus, member states’ dominant reasoning follows the goal to avoid adaptation costs for their economy.