Article 6 of the Kyoto Protocol enables Annex 1 Parties to agree to jointly undertake emissions saving or sink enhancing activities, with credits arising from cross border investments transferred between them. Joint Implementation (JI) is effectively an alternative project-based mechanism for trading emissions between countries with a cap. Instead of directly purchasing emission rights, i.e. assigned amount units (AAUs), a country gains emitting permits through funding a part of a project activity which reduces greenhouse gas (GHG) emissions or enhances removals by sinks. This report summarises the development of Joint Implementation mechanism thus far, and discusses its possible futures.