The paper gives results of an evaluation of the formation and removal of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) at various locations throughout the Montgomery County South municipal waste incinerator in Dayton, OH. It is a mass burn refractory incinerator, consisting of an ignition chamber, rotary kiln, mixing chamber, water quench chamber, electrostatic precipitator (ESP), and stack. Three tests at each of six test conditions were used to evaluate the effects of ESP inlet temperature, sorbent injection, and combustion temperature on pollutant formation and emission. Test results indicated two sources of PCDD/PCDF formation: the combustor upstream of the mixing chamber and the ESP. PCDD/PCDF leaving the combustor appears to be associated predominantly with entrained particulate matter (PM) with particles larger than 10 micrometers. Increases in PCDD/PCDF concentrations across the ESP were found at lower temperatures (148 C) than previously reported. Indicated PCDD/PCDF formation rates in the ESP were highly dependent on ESP inlet temperature.