The taxation of different sources and uses of energy (particularly those that give rise to emissions of greenhouse gases) will play a key role in governments’ efforts to mitigate the scale of global warming and climate change. At present, effective tax rates vary widely across different sources and uses of energy within countries, as well as across countries. This publication provides the first systematic statistics of such effective tax rates – on a comparable basis - for each OECD country, together with ‘maps’ that illustrate graphically the wide variations in tax rates per unit of energy or per tonne of CO₂ emissions. These statistics and maps should be an invaluable tool for policymakers, analysts and researchers considering both domestic fiscal reform in response to climate change and other environmental challenges (e.g. to achieve emissions reductions targets most cost-effectively) and wider international responses.