The report describes the methodologies and data bases used to develop species allocation factors and data processing software used to develop the 1985 National Acid Precipitation Assessment Program (NAPAP) Modelers' Emissions Inventory (Version 2). Species allocation factors were developed to convert annual emissions estimates of hydrocarbons, nitrogen oxides (NOx), and total suspended particulates (TSP) into more resolved classes to be used in modeling and assessment activities. The factors were used to divide: the hydrocarbon estimates in the annual inventory into 32 representative chemical classes based on common reactivity and product species, the NOx estimates into NO and NO2, and the TSP estimates into 15 classes based on component species and size ranges. Temporal, spatial, and pollutant species allocation factors have been developed to convert annual emissions data into resolved modeling formats suitable for use as input to regional transport models such as the Regional Acid Deposition Model. The level of resolution required for the allocation factors was defined by the modelers based on analyses of model performance and emissions data bases.