The report describes the model logic and data sources for Version 3.0 of the Process Model Projection Technique (PROMPT), one of four stationary source emission and control cost forecasting models developed for the National Acid Precipitation Assessment Program (NAPAP). PROMPT projects air pollution emissions (SO2, sulfates, and NOx) and costs for industrial combustion and industrial processes (e.g., process heaters, furnaces, dryers, kilns, engines, turbines, and wood-fired boilers). PROMPT excludes emissions from the combustion of natural gas, distillate and residual fuel oil, and coal in industrial boilers. The outputs are provided for 1980 (baseline), 1985 (forecasted, not actual), 1990, 1995, 2000, 2010, 2020, and 2030. The data sources used to develop PROMPT Version 3.0 predate the release of the final 1980 NAPAP Emissions Inventory.