What is the role played by institutions and organizations in the initial phase of an international negotiating process, when problems are defined, agendas structured and the process of negotiating a regime is put on track? Why do some environmental problems gain higher priority in international politics than others, even though the latter are perhaps just as severe in ecological terms? To what extent do institutions and organizations contribute to global environmental problems entering the international policy agenda, and what role do they play in the agenda-setting phase of a policy cycle? To analyse these issues, the Council has selected three key problems of global change (ozone depletion, climate change, soil degradation) that are regulated internationally with differing degrees of effectiveness and – this is decisive for their selection – have succeeded in attaining different levels of priority on the international policy agenda. Beyerlin (2000) provides a comprehensive overview of international environmental law.