Many of the major environmental challenges facing governments and societies today are collective problems, calling for joint solutions. However, even when effective solutions can be found only through joint efforts, international cooperation is often hard to establish and maintain. This makes it all the more important to understand the conditions for "success" and the causes of "failure". This text examines some of the political mechanisms at work in the formation and operation of international environmental regimes. What are the major factors that shape the national positions that governments bring to the negotiating table? How do the international institutions and negotiation processes through which these preferences and positions are adjusted and aggregated affect outcomes? What are the main mechanisms determining whether or not international environmental agreements are successfully implemented at the domestic level?