The report quantifies the U.S. sulfur oxide (SOx) emissions problem, and attributes it, proportionately, to its various significant sources. It briefly presents the regulatory framework applicable to the control of SO2 air pollution, and mentions projected regulatory changes. It cites various SOx control technologies, but emphasizes flue gas desulfurization (FGD). It briefly describes processes for currently operating full-scale FGD systems. It discusses the current status of FGD systems applied to utility and industrial boilers, with emphasis on utility systems. It gives the number of units and controlled capacity for systems currently operating, under construction, and planned. It discusses major problems incident to the application of FGD systems, with respect to their impact on system dependability. It tabulates capital and annual costs of FGD systems for actual operating systems, and presents adjusted costs for these systems to permit system/type comparisons. It also gives cost estimates for generalized or model plant designs, and compares these estimates with reported and adjusted actual system costs. (Projected growth of FGD use is based on currently planned utility units and more stringent regulations.) The report compares these projected growth rates of utility FGD applications with a projected need for FGD. The status of FGD systems in Japan is also described.