The paper gives results of an early-1989 investigation of the effect of changing combustion and flue gas cleaning (FGC) system variables on the performance of these systems. Using information from earlier characterization tests at the same site (Mid-Connecticut facility in Hartford), performance data on a refuse-derived fuel (RDF) combustor and its lime spray dryer absorber/fabric filter (FGC) system were obtained under good, intermediate, and poor combustor operation and high, normal, and low sulfur dioxide (SO2) control by the FGC system. The independent combustion system variables included steam load, air supply rate, and its distribution. For the FGC system, the outlet gas temperature from the spray dryer absorber served as an easily measurable surrogate for the approach to saturation temperature, while SO2 concentration in the flue gas at the fabric filter outlet continuously represented the lime stoichiometry. Test data included acid gas, trace organic, trace metal, and particulate concentrations, as well as material collection for the determination of ash/residue composition and production rates. In addition, process data and RDF feed and ash/residue generation rates were obtained. Correlations between combustion conditions and furnace emission of organic pollutants are presented.