The report addresses two major questions in air pollution control: What emission control strategy should be used by the states to achieve their air quality goals. How can air quality effects of changing land use patterns to predicted. A comparison of three alternate emission control strategies as applied to the St. Louis Air Quality Control Region, is presented. The strategies are: A conventional set of emission source-category standards. A rollback strategy, and A least-cost strategy. Study results include regional costs, air quality achieved, emission reductions, plots of pollutant concentration levels (isopleths), and a measure of benefit. The report also presents a description and brief analysis of a simple procedure by which a diffusion model can be used to predict the (air Quality) consequences of shifting land use, without incurring the expense of continually re-running the entire model.