Modern democratic governance occurs only rarely via traditional Weberian hierarchies or pure ‘markets’. Rather, public policies are made via some kind of hybrid arrangement involving a range of different actors, including some representing private or non-governmental institutions. The concept of policy networks - clusters of actors, each with an interest, or ‘stake’ in a given policy sector and the capacity to help determine policy success or failure - has been developed and refined as a way to try to describe, explain and predict the outcomes of policy-making via such hybrid arrangements. Governance by policy network is rife at the level of the European Union because it is such a highly differentiated polity which is dominated (in important ways) by experts and highly dependent on ‘government by committee’. Research on EU policy networks has produced useful results but we remain some distance away from an agreed, plausible ‘theory’ of policy networks.