National circumstances (CN) present geographic characteristics, climate factors, natural resources, the profile of the legal, institutional and legal framework, the climate profile, the demographic and socio-economic profile, all of which are likely to be affected by climate change or reduce the possibilities of adapting to climate change. This chapter forms the basis of analysis for the various sectoral studies, in particular greenhouse gas (GHG) inventories, vulnerability and adaptation and mitigation studies carried out under the United Nations Framework Convention on Climate Change (UNFCCC).