This article analyzes the conditions for mobilizing the science base for development of public policy. It does so by focusing upon the science-policy interface, specifically the processes of direct interaction between scientists and scientifically trained experts, on the one hand, and agents of policymaking organizations, on the other. The article defines two dimensions – cognitive distance and expert autonomy – which are argued to influence knowledge exchange, in such a way as to shape the outcome. A case study on the (...) implementation of congestion charges in Stockholm, Sweden, illustrates how the proposed framework pinpoints three central issues for understanding these processes: Differentiating the roles of, e.g., a science-based consultancy firm and an academic environment in policy formation; Examining the fit between the organizational form of the science-policy interface and the intended goals; and Increasing our understanding of when policymaker agents themselves need to develop scientific competence in order to interact effectively with scientific experts. (shrink)