Abstract:This paper examines past experience in controlling emissions of sulphur dioxide (SO2) and nitrogen oxides (NOx) from coal-fired electric power plants. In particular, we focus on US and worldwide experience with two major environmental control technologies: flue gas desulphurisation (FGD) systems for SO2 control and selective catalytic reduction (SCR) systems for NOx control. We quantitatively characterise historical trends in the deployment and costs of these technologies over the past 30 years, and use these data to develop quantitative ‘experience curves’ to characterise the rates of cost reduction as a function of cumulative installed capacity of each technology. We  explore the key factors responsible for the observed trends, especially the development of regulatory policies for SO2 and NOx control and their implications for environmental control technology innovation. We further discuss some of the key technical innovations that have contributed to cost reductions over time. Finally, we discuss the relevance of these findings to other environmental issues of current interest, especially the outlook for technological progress in carbon capture and sequestration technologies applicable to fossil fueled electric power plants.