The focus of emission inventory activities within the National Acid Precipitation Program (NAPAP) is to estimate emissions of pollutants of concern to the acid deposition phenomenon. Electric utilities emit a large share of total acid deposition precursor emissions. The purpose of the study was to produce a 1980 utility data base that met the needs of NAPAP task groups for utility data. Special emphasis was placed on meeting data needs of atmospheric modelers, emissions forecasters, and policy analysts. The product of the analysis, the NAPAP Utility Reference File, now serves as the source of emissions data for the 1980 NAPAP emission inventory. It also serves as the source of operating and economic data for utility simulation models. Because both fossil and non-fossil units are included, the total number of units is more than 11,000. Utility NOx and SO2 emission estimates made using NAPAP Utility Reference file data for 1980. Six data files are included on the tape: four NAPAP update files and both the existing and announced Unit Inventory files. These are derivative files of the NAPAP Reference Utility Files (NURF). These files contain 1980-based electric utility related unit-level data. The NAPAP update files include corrected and added data on all electric utility generating units, fuel specific emission data, stack parameter data, and announced or coal-converting units. The existing Unit Inventory contains unit-specific data on larger generating units and aggregated information on smaller ones: the announced Unit Inventory contains data on those units coming on-line or planned for coal conversion data after 1980.