To date, most of the focus on greenhouse gas emission reductions has been on energy-related CO2 emissions. This is understandable since CO2 emissions currently account for about 82 percent of the total US greenhouse gas emissions weighted by 100-year global warming potentials (EPA, www.epa.gov/globalwarming/publications/emissions, 2001a).(1) However, a number of analyses suggest that the non-CO2 greenhouse gases included in the Kyoto Protocol-methane, nitrous oxide, and the high-GWP (global warming potential) gases (HFCs, PFCs, and SF6)-can make a significant contribution to cost-effective emission reductions for the US and other countries. Our current estimate for the US is a reduction in non-CO2 emissions of 105 million metric tons of carbon equivalent (MMTCE) at $50/ton carbon equivalent in 2010. This paper provides a perspective on the current and projected emissions of greenhouse gas; outlines the potential methods for achieving emissions reductions for various sources; and summarizes several recent studies on the cost of reductions for the US and other countries. Although the paper does not specifically address the potential for reductions of these gases in individual countries outside the US and the European Union, its findings are generally applicable to many countries. Published by Elsevier Science Ltd.