The article discusses the current status of commercial flue gas desulfurization (FGD) processes applied to coal-fired utility boilers in the U.S. Major objectives of the work were to examine the impacts of the 1979 New Source Performance Standards on FGD system design and operation, and to identify recent improvements in the technology. In the 4 years since promulgation of the NSPS, the wet limestone process has been selected by utilities for 75% of the new plant capacity. During this time, 77 plants representing over 37,000 MW of capacity have selected FGD systems. Several major trends in the design of limestone systems have become fairly standardized. Nearly all new systems are being built with spare absorber modules, to qualify for the NSPS emergency bypass provisions. The predominant absorber design is the open spray tower, due to minimal maintenance requirements. Forced oxygen to produce gypsum solids, which can then be landfilled, is being incorporated in many new units. The spray drying process has been selected for 15% of the new sites in the last 4 years. The remaining throwaway and regenerable systems have not experienced any significant increases in application. Finally, organic acid addition has been successfully demonstrated on limestone systems to improve SO2 removal and system reliability. It is being used at two sites to upgrade older systems.