There is a growing interest in ‘evidence-based policy making’ in the UK. However, there remains some confusion about what evidence-based policy making actually means. This paper outlines some of the models used to understand how evidence is thought to shape or inform policy in order to explore the assumptions underlying ‘evidence-based policy making.’ By way of example, it considers the process of evidence seeking and in particular the systematic review as a presumed ‘gold standard’ of the EBP movement. It highlights some of the opportunities and challenges represented in this approach for policy research. The final part of the paper outlines some questions of capacity that need to be addressed if the social sciences are to make a more effective contribution to policy debate in Britain.