The paper gives an overview of EPA's testing of the adipic-acid-enhanced limestone flue gas desulfurization (FGD) process. Extensive research has determined that adipic acid, used as an additive to a limestone FGD system, improves system performance. Both SO2 removal and limestone utilization can be greatly increased by the buffering effect of adipic acid. Successful testing in laboratory-, bench-, pilot-, prototype-, and full-scale systems has demonstrated the benefits of this technology for new and retrofit applications. Although adipic acid degrades in the scrubber, no significant operating problems or environmental impacts have been identified. Economic estimates show the adipic-acid-enhanced limestone FGD system to be economically attractive, compared to conventional FGD systems. In addition, further research is underway to decrease the cost of using additives in FGD systems.