A greenhouse gas emissions inventory was conducted for Chicago and its metropolitan region for the years 2000 and 2005. Emissions of carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride totaled 34.7 million metric tons of carbon dioxide equivalents (MMTC0₂e) in Chicago in 2000 with 91% of emissions attributable to the indirect emissions associated with electricity consumption, the direct emissions of natural gas use, and the direct emissions of the transportation sector. A portfolio of 33 potential emissions reduction strategies was analyzed that, implemented together, could meet Chicago's target of reducing greenhouse gas emissions to 25% below 1990 levels by 2020. The largest potential for reduction is found in the areas with the largest emissions—energy use in buildings and transport. Compared to its metropolitan region, Chicago is found to have existing transportation efficiencies on a per household basis that can be an example for other communities.