The Energy Research Centre of the Netherlands (ECN) has been developing the Marginal Abatement Cost (MAC) curve for Non-Annex I countries since 1999. The curve results from compiled data of bottom-up country based studies at regional sectoral level and presents greenhouse gas (GHG) abatement opportunities by 2020. MAC curves describe the expected marginal cost and GHG abatement potential of several mitigation options. In addition to other tools and country specific assessments, these curves are tools for policy makers seeking for sectoral overviews of possible cost-effective mitigation options. The MAC curve tool developed by ECN covers the GHG abatement potential by means of over 1100 country-technology combinations in the non-Annex I region. This curve is updated whenever new relevant studies are published.