This paper surveys economic aspects of the Kyoto Protocol, the Treaty adopted to control emissions of the greenhouse gases that contribute to climate change. The first part focuses upon the structural aspects of the agreement, with particular attention to the long-term conception of the Treaty and its use of market-oriented instruments unprecedented in an international treaty of this scope. The second part then examines the actual commitments adopted for the first period, and the impact of US withdrawal upon the economics of these commitments as mediated through the ‘flexible mechanisms’. It is noted that the emerging behaviour of states under Kyoto is very different from that assumed in economic modeling studies—countries are focusing first upon domestic action and will resort to the mechanisms mainly as a fallback option to secure compliance, not as a route to minimizing costs irrespective of other considerations. This may have important implications for understanding the practical economics of designing international market mechanisms, and for the next steps that might be considered under Kyoto.