The report provides, to states and other participants (e.g., Regional Offices, Headquarters, other federal agencies) and users of the Area and Mobile Source subsystem (AMS), an understanding of the estimation procedures that will be used by the national component of AMS to generate emissions estimates for area and mobile source categories. It discusses general methodology and assumptions as well as the original source of algorithms, activity levels, and emission factors necessary to calculate emissions for each area and mobile source in AMS. The report presents methodologies for all identified sources not defined as point sources. Area and mobile sources are divided into seven major groups: stationary source fuel combustion, mobile sources, industrial processes, solvent utilization, solid waste disposal, natural sources, and miscellaneous area sources. Historically, these methodologies have been referred to as the National Emissions Data System (NEDS) methods and to some extent are documented in area source documentation for the 1985 National Acid Precipitation Assessment Program (NAPAP) inventory; however, the NAPAP documentation does not include certain initial data calculations. In addition, over the years numerous changes have occurred to the sources of the data that "feed" these methodologies. These initial data calculations and source data changes are included in the report.