The report gives results of economic evaluations of three gypsum-producing flue gas desulfurization processes: advanced limestone (in-loop forced oxidation with adipic acid additive), Davy S-H (lime), and Dowa (aluminum sulfate, limestone). For a 500-MW power unit burning 3.5% sulfur coal and meeting the 1979 New Source Performance Standards, capital investments in 1982 costs are $93 million ($186/kW) for the advanced limestone process, $116 million ($231/kW) for the Davy S-H process, and $121 million ($243/kW) for the Dowa process. First-year annual revenue requirements in 1984 costs for these processes are $26, $33, and $32 million (9.4, 11.9, and 11.7 mills/kWh), respectively. The lower capital investment and annual revenue requirements of the advanced limestone process are due in part to the use of adipic acid, which allows partial scrubbing at 95% removal. The Davy S-H process has slightly higher annual revenue requirements than the Dowa process because lime is used, instead of limestone. Changes in power unit size and coal sulfur content affect the costs of all three processes similarly. The Davy S-H process is more sensitive to raw material costs because lime is used. Landfill waste disposal is a minor cost element in all three processes.