Pollution control invariably involves a complex relationship between acceptable costs and acceptable levels of environmental impact. This paper presents abatement costs and environmental impacts for various processes for the treatment of sulphur dioxide gases from metallurgical smelters in Australia. This information is then presented in ＇cost-environmental impact index plots＇ developed by the authors as a means of presenting economic and environmental impacts together, using a flexible system boundary. In this case the system boundary has been extended to include the utilization of desulphurization products and downstream fertilizer production. The cost-environmental impact index plot can be used in project evaluation to assist the choice of the best processing strategy and to examine the effects of different variables, The plot is also shown to be useful for examining process variations in a base case technology, by identifying the cost-effectiveness of incremental improvement in environmental quality.