This chapter investigates the design features which influence how organized science contributes to effective international regimes. Work on epistemic communities found that organized networks of scientists and experts shaped international environmental governance and contributed to the effectiveness of international regimes, particularly in the environmental domain. Studies of marine governance regimes and stratospheric ozone suggest a more one-sided model in which decision makers defer to the authority of science provided by international panels and the United Nations Environment Programme (UNEP). Science panels have become de rigueur for providing information and usable knowledge for environmental governance. International science panels are established by states to provide knowledge about global and transboundary risks. The initial design of science panels in the 1970s followed trial-and-error learning by UNEP in developing international environmental regimes. Fisheries cases show more variation in effectiveness of fisheries regimes than generally thought, as a consequence of variations in the design of the associated science panels.