This book furthers the ongoing theoretical development of the multiple streams framework, assessing its applicability to European Union (EU) policy-making processes. It systematically defines and identifies functional equivalents for all of the framework’s core concepts at the EU level and extends the framework in order to explain agenda-setting and decision-making. Furthermore, the book derives a set of explicit hypotheses to empirically assess the extent to which the (modified) framework is able to explain timing, agenda prominence, and policy change (or a lack thereof) for the EU natural gas directives passed in 1998, 2003, and 2009. The analysis documents that the framework is well-suited to explain the EU policy process in general and reveals where additional theoretical refinements are required.