As part of the National Acid Precipitation Assessment Program (NAPAP), the U.S. Environmental Protection Agency (EPA) identified the need to generate emissions factors for volatile organic compound (VOC) emissions for about 1,800 source classification categories (SCCs). Additionally, emission factor development was needed for nitrogen oxides (NO[subscript x]), sulfur oxides (SO[subscript x]), and VOCs for SCCs that states have used to report emissions. Each SCC represents a specific process or function that is logically associated with a point source of air pollution. The objective of this effort was to estimate VOC emission factors for all SCCs where VOC factors were previously absent, and to develop NO[subscript x] and SO[subscript x] emission factors for SCCs that states had reported as emission sources. This report includes emission factor estimates for VOCs, NO[subscript x], and SO[subscript x] which were developed from a variety of readily available information. Emission factors for particulate matter (PM) and carbon monoxide (CO) from AP-42 Fourth Edition and Supplement A are also presented. Data gathered during numerous standards-setting activities as well as data provided from state emissions inventory data bases were used to calculate the new emission factor estimates. Technology transfer of emission factors for similar processes in different industries provided emission factor estimates for source categories where no data were available. A list of all valid SCCs used in the 1985 NAPAP Emissions Inventory, as well as about 90 SCCs which have been added to the inventory since October 1985, is included along with all emission factor estimates developed through April 1987.