The report documents the development of spatial allocation factors to apportion National Acid Precipitation Assessment Program (NAPAP) area source emissions from counties to individual grid cells for input to the Regional Acid Deposition Models (RADM) and Regional Oxidant Models (ROM). The development effort focused on creating a variety of spatial surrogates to allow the user maximum flexibility in assigning area source emissions to modeling grid cells. The surrogates are used to represent the sub-county distribution of area source emissions for each category. Fourteen surrogate indicators were developed for use with the NAPAP inventory based on housing, population, and land use data. Fortran programs were developed to generate the spatial factors. These programs are available on a companion magnetic tape. The user can specify processing options and grid definition by means of control option files accessed by the programs. Once the sub-county distribution of each surrogate is determined, area source emissions categories are matched to the most appropriate surrogate. The resultant Spatial Allocation Factor File is input to the Spatial Allocation Module of the Flexible Regional Emissions Data System.