Given the scientific and social importance attached to productive interactions between science and policy practices, there is a striking lack of insight into current knowledge practices and the dilemmas they lead to. Our special issue can’t solve this deficiency but it can provide an impetus for opening up current knowledge practices, reflect on the role of science in them and instigate a more systematic exchange of methods. A warning is given for the reification of boundary work and Gabrielle Bammers’ Implementation and Integration Sciences is introduced as framework for the analyses.