Air pollution control regulations already implemented or being considered for implementation require substantial investment of capital to remove the sulfur oxides from copper, lead, and zinc smelter gases. As a result, there will be an attendant increase in production costs and possibly an associated increase in the price of these metals to the consumer. The total investment and any resulting metal price increase will depend upon the control regulations that ultimately will be adopted by the individual states. Controversy has arisen between the metals industry and governmental control agencies regarding the status of stack gas desulfurization technology and the ability of industry to control sulfur oxide emissions to the degree proposed by some of the more stringent regulations currently under consideration. This paper evaluates the problems involved in achieving various degrees of control over smelter sulfur oxide emissions and the technology available to accomplish the task of assuring clean air. The estimated cost of compliance is reviewed for the copper, zinc, and lead industries, but principal attention is given to the copper situation.