Although the powerful have always sought advice from the knowledgeable, it took the appeal of the policy sciences movement of the late 1940s and onward to build and consolidate a veritable industry of policy analysis and advice.1 One of the hallmarks of this development was the advent of institutes that were exclusively devoted to produce research-based policy arguments and to inject these into the policy-making process. These organisations were referred to as ‘think tanks’. Half a century later, the project of the policy sciences movement has been amply criticised, and has mutated into various philosophies of policy analysis, each harbouring distinct and often conflicting perspectives on the nature and role of (scientific) knowledge in the battle of arguments that is public policy-making. The first wave of the policy sciences movement's privileging of science-based policy has not disappeared. In fact it is currently experiencing a revival under the banner of ‘evidence-based policy’. But it has to compete with other views of public policy-making which deconstruct the authority claim of scientific knowledge, emphasising instead its contestability. Yet there are now more organisations that refer to themselves, or can be labelled, as ‘think tanks’ than ever before. Why? And what does it mean to be a ‘think tank’ in the post-positivist era and in the increasingly boundary-less, highly networked societies of today? This article first surveys recent developments in the world of think tanks as reported by the international literature on the subject, and then examines the implications for understanding the nature and role of Australian think tanks.