The lack of previous research into political interest groups and taking into account policy-specific and institutional context characteristics is largely due to research designs that have been primarily focused on a small number of policy debates, with the result that contextual characteristics were largely held constant. This book brings together articles from different modules that are part of a larger European Collaborative Research Project, INTEREURO, carried out by research teams in nine different countries under the auspices of the European Science Foundation. The main goal of the book is to analyse strategies, framing and influence processes for a set of 125 legislative proposals submitted by the European Commission, in an effort to better understand the involvement of interest organizations in the decision-making process of the EU. Contributors draw on sophisticated and innovative policy-driven samples of interest group mobilization, allowing them to account systematically for how policy-specific and institutional context factors shape mobilization, lobbying strategies and influence of interest groups on public policy debates in the EU. In this way, the book makes an important contribution to the study of interest groups in the EU and represents the breadth of positions taken in the current literature. This book was originally published as a special issue of the Journal of European Public Policy.