The paper gives results of experiments in a 0.1 MW pilot plant to determine the effects of high concentrations of chloride ions and dissolved salts on flue gas desulfurization (FGD) scrubbing chemistry, both in the natural and forced oxidation modes of operation. (Note: The tightly closed water loops in FGD systems promote the buildup of soluble salts in the recirculating scrubbing liquor.) As the concentration of calcium chloride increased, significant decreases in sulfur dioxide (SO2) removal efficiency were measured. The decreases are shown to be independent of absorber inlet SO2 concentration and liquid/gas ratio, but not independent of degree of oxidation and excess limestone in the slurry. A semi-empirical model, that explains both natural and forced oxidation SO2 removal data, was developed. An overview of the problem and a summary of test results to date are given in detail.