Landfill Gas Emissions Model (LandGEM) estimates air pollutant emissions from municipal solid waste (MSW) landfills. The model can be used to estimate emission rates for methane, carbon dioxide, nonmethane organic compounds, and individual air pollutants from landfills. It can also be used by landfill owners and operators to determine if a landfill is subject to the control requirements of the federal New Source Performance Standard (NSPS) for new MSW landfills or the emission guidelines for existing MSW landfills. The model is based on a first order decay equation and can be run using site-specific data for the parameters needed to estimate emissions or, if no site-specific data are available, using default values: one set based on the requirements of the NSPS and emission guidelines, and the other based on emission factors in EPA's Compilation of Air Pollutant Emission Factors, AP-42. The former estimates are conservative and can be used to determine if the landfill is subject to control requirements of the NSPS and emission guidelines. The latter estimates are more representative, and can be used to produce typical estimates in the absence of site-specific test data. Current default values in the model are those recommended by the NSPS and AP-42 as of September 1997.