A central issue in negotiations under the United Nations Framework Convention on Climate Change (UNFCCC) is how best to provide for the measurement, reporting and verification (MRV) of parties’ mitigation actions and support. This brief describes and evaluates existing requirements under the UNFCCC and the Kyoto Protocol, and outlines recommendations for building on these mechanisms to establish a more robust MRV system. This enhanced system should include: significantly strengthening the existing system of reporting and expert review, and establishing a new mechanism for peer review of mitigation actions. Peer review and expert review would together constitute the international “consultations” and “analysis” envisioned in the Copenhagen Accord.