This article sets out core issues to be addressed in implementing the trading mechanisms of the Kyoto Protocol. Firstly, this article focuses upon the issues surrounding the intergovernmental exchange of assigned amounts, and argues that this should be governed by a principle of emissions conservation, a rule of shared liability, and a guideline that transfers should represent real emission reductions. Modalities for implementing this guideline are discussed. The article then sets out issues of accountability arising from industry-level emissions trading, noting tensions between industry and government objectives that may best be resolved through intermediary agencies. Finally, the article considers the parallels and differences in the derivative mechanisms of Joint Implementation and the Clean Development Mechanism.