The paper gives results of experiments in a pilot-scale rotary kiln incinerator simulator, where a mixture of chlorinated and brominated surrogate waste was burned in the presence of injected fly-ash from a coal-fired utility boiler. Measurements were made of semivolatile products of incomplete combustion (PICs), polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) and mixed bromo-chloro dibenzo-p-dioxins and furans (PXDDs/Fs). The data have been analyzed statistically so that variability in the PCDDs/Fs can be accounted for by variation in the semivolatile PICs, particularly the chlorobenzenes (CBz) and chlorophenols (CPh). In addition, a statistical analysis was performed to investigate the variability of the PXDDs/Fs as a function of the concentrations of the semivolatile chlorinated, brominated, and mixed bromo-chloro organics.