There are conflicting claims about the greenhouse friendly nature of coal seam gas in Australia. In this article, Colin Hunt finds that the differences turn on assumptions about the quantity of gas that escapes to the atmosphere from coal seam gas operations and the gas’ global warming potential. He argues that both better measurement of the fugitive emissions of coal seam gas and an official update of its greenhouse potency are required. These recommendations have important implications not only for meeting Australia’s greenhouse targets but for the tax rates on emissions under the Clean Energy legislation.