A 71-step reaction-kinetic model for the formation of 1,3,6,8-and 1,3,7,9-tetrachlorodibenzo-p-dioxins (TCDDs) from the oxidation of 2,4,6-trichlorophenol in the presence of hexane is developed based on experimental data and a simpler model that was previously published in the literature. The rate of reaction of phenoxyl-radicals with molecular oxygen has recently been experimentally demonstrated to be at least five orders of magnitude slower than the rate used in the previous model. With this correction, inclusion of radical-radical recombination reactions of 2,4,6-trichlorophenoxyl-radicals, and other minor modifications, the revised model yields satisfactory agreement between experimental and predicted concentrations of TCDDs above 900 K. The results of this study indicate that high-temperature, gas-phase reactions of chlorinated phenols that contain an ortho-chlorine will form poly-chlorinated dibenzo-p-dioxins (PCDDs) in yields approximately four to five orders of magnitude greater than believed, based on the previous modeling results. (C) 2003 The Combustion Institute. All rights reserved.