The report describes the development of a model for estimating emissions of volatile organic compounds (VOCs) from petroleum refineries and synfuel plants. The model, responding to a need to define a consistent and comprehensive approach for estimating VOC emissions from these two sources, is a modular technique in which the entire spectrum of potential VOC emissions sources was defined in a number of process and utility modules. Each module represents a process or auxiliary unit. The user of the model provides emission source counts and other process information, or uses provided default values. Emissions are calculated using emission factors for each source type. Detailed examples of the application of the model to both refineries and synfuel plants are presented. Such estimates, of considerable interest to the EPA, industry, and the public, are needed in the preparation and review of Environmental Impact Statements (EIS) and permits required by the Clean Air Act. Responding to this need, several studies have been made of VOC emissions, particularly from refineries. Methods for estimating VOC emissions and the results of VOC emissions tests have been published in various journals and at various forums.