The reactions of (halogenated) phenoxy radicals with (ortho) chlorinated or brominated phenols may play: a role in "dioxin" formation mechanisms. Therefore, we have recently investigated the model reaction (la) by using the slow combustion of phenol/chlorobenzene mixtures in a well-stirred reactor. This study has now been extended to include bromobenzene. Phi O + Phi X --> Phi O Phi + X, (a) X = Cl, (b) X = Br 2 Phi O --> DF The rate coefficient for reaction (la) was derived from the determination of the direct reaction product diphenylether (Phi O Phi) in comparison to dibenzofuran (DF) which is formed in the competing self-reaction (2) and found to obey (728 < T < 984 K) k(1a) = 4.8 * 10(8) exp(-24.5 kcal/mol/RT) L/mol s. This method with Phi Br (reaction Ib) instead of Phi Cl is ambiguous since the HBr produced from the slow combustion of Phi Br affects the overall rate coefficient for Df: formation from phenoxy radicals, Nevertheless, we have carried out Phi OH/Phi Br experiments under conditions similar to those for Phi OH/Phi Cl. The measured DI: and Phi O Phi, yields suggested that reactions (Ib) and (la) have nearly equal rates. To obtain a better insight we have investigated the co-combustion of Phi Br/Phi Cl mixtures with Phi OH, i.e., the reaction Phi O + (Phi Br was measured in competition to Phi O + Phi Cl (805 < T < 953 K). Since the direct reaction product is in both cases Phi O Phi one of these two reactions has to be labelled and this was achieved by using deuterated bromobenzene, d(5)-Phi Br. The respective diphenylethers were measured by GC/MS. Some H/D scrambling at higher temperatures was accounted for. The rate coefficient for reaction (Ib) was found to obey k(1b) = 1.4 * 10(8) exp(-21.4 kcal/mol/RT) L/mol s. This rate coefficient is much too small for the high yields of polybrominated dibenzodioxins as observed by Sidhu et al. (1995) in flow reactor experiments with 2,4,6-tribromophenol. This means that a radical-radical reaction of(ortho) brominated phenoxy radicals is the most likely source of halogenated dioxins, in analogy to the related case of slow combustion of 2,4,6-trichlorophenol.