The report describes the relative importance of landfills to global warming and identifies the major sources of uncertainty with current emission estimates. It also provides an overview of EPA's research program on global landfill methane, including developing more reliable estimates of global landfill methane emissions, characterizing the current state of technology for controlling and utilizing landfill methane, and demonstrating innovative technologies for mitigating and utilizing landfill methane. Landfills are considered a major source of methane, which is a potent greenhouse gas. Because this source is amenable to cost effective control measures, research designed to reduce the uncertainty associated with methane emissions estimates has been given high priority.