The National Emissions Report summarizes annual cumulative estimates of source emissions of five criteria pollutants: particules, sulfur oxides, nitrogen oxides, volatile organic compounds, and carbon monoxide. Source emissions data are reported to the U.S. Environmental Protection Agency under provisions of Section 110 of the Clean Air Act, as amended 1977, and EPA regulations, Title 40, Code of Federal Regulations, Part 51.321. Summary data are presented for the Nation as a whole, for individual States, and for Air Quality Control Regions and for individual interstate portions thereof. The data compilations result from the operations of the National Emissions Data System (NED), which functions as a component of the comprehensive EPA air information system--the Aerometric and Emissions Reporting System (AEROS). AEROS is managed by the National Air Data Branch, Emissions Standard Division, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, at Research Triangle Park, North Carolina.