The paper gives the scope and methodology of EPA/AEERL's methane emissions studies and discloses data accumulated thus far in the program. Anthropogenic methane emissions are a principal focus in AEERL's global climate research program, including three major sources: municipal solid waste landfills, coal mines, and natural gas systems. A major emphasis in the landfill program is measurement of emissions from operating landfills and calculation of country-specific emissions. Landfill methane emissions are not estimated, but factors affecting emissions are discussed and estimates developed by others are provided. For coal mines, existing data collected by other researchers are combined with EPA data on emissions from surface mines, coal handling systems, and abandoned mines to provide an estimate of global emissions of 46 Tg/yr. Methane from natural gas production, transmission, and distribution systems is estimated to be 4.4 Tg/yr for the U.S.