Lawmakers could increase federal revenues and encourage reductions in emissions of carbon dioxide (CO2) by establishing a carbon tax, which would either tax those emissions directly or tax fuels that release CO2 when they are burned (fossil fuels, such as coal, oil, and natural gas). Emissions of CO2 and other greenhouse gases accumulate in the atmosphere and contribute to climate change-a long-term and potentially very costly global problem. The effects of a carbon tax on the U.S. economy would depend on how the revenues from the tax were used. Options include using the revenues to reduce budget deficits, to decrease existing marginal tax rates (the rates on an additional dollar of income), or to offset the costs that a carbon tax would impose on certain groups of people. This study examines how a carbon tax, combined with those alternative uses of the revenues, might affect the economy and the environment.