More than 10 years of climate policy negotiations have produced the Kyoto Protocol, the first legally binding international agreement on climate protection, which may enter into force in the near future. Opponents to the Protocol have condemned it as a "deeply flawed agreement that manages to be both economically inefficient and politically impractical" (McKibbin and Wilcoxen 2002, p.107). This article sustains a more positive perspective on the Kyoto architecture. Key elements of the Protocol comply with basic economic principles. The Protocol is based on a control mechanism that allows iterative adjustment and movement toward evolving goals. A system of periodically negotiated five-year periods supports a flexible approach that allows policy-makers to adjust their decisions according to better information obtained in the future. The Protocol constitutes the first international environmental agreement that builds on market based instruments to determine cost-efficient responses to the undisputed need for GHG abatement. Last but not least, Kyoto-after tough bargaining-came up with a burden-sharing scheme for the first commitment period that all major Parties (with exception of the US) have accepted as a "fair" compromise, hereby reflecting historic responsibilities for the greenhouse gas externality as well as ability to pay. On the other hand, it must be clearly stated that the Kyoto Protocol-as it stands now-has not achieved a decisive breakthrough in international climate policy. First, sink credits, hot air through emissions trading and, in particular, U.S. repudiation will make Kyoto ineffective in environmental terms during the first commitment period. Second, it has yet to be negotiated what must be done after the first commitment period. The major challenge for future Post-Kyoto climate policies remains as to how international cooperation on the provision of climate protection (as a global public good) can be promoted. In the first place, this requires incentives for developing countries to participate. Ultimately, this comes down to how abatement duties-or emission entitlements-should be allocated across countries over a longer time horizon. In the second place, a credible system of direct or indirect sanctions must be developed that can deter free-riding. .