The analysis of gas-phase mercury speciation in combustion gases containing bromine and SO2 was studied using a commercial mercury analyzer coupled with several different wet conditioning systems; the latter allowed the measurement of total or elemental mercury in the combustion gases. The total side of the conditioning system was modified to decrease measurement bias in total mercury by replacing an aqueous tin chloride solution (2 wt % SnCl2 and 3 wt % HCl) with a solution of hydroxylamine hydrochloride and sodium hydroxide (4 wt % NH2OH-HCl and 20 wt % NaOH). This change reduced measurement bias in total mercury in the presence of 50 ppm bromine species (as HBr equivalent) from 60 to 15%. Additional improvements in total mercury recovery were obtained by frequently cleaning the glass walls of the chiller, an essential component of the mercury analysis train. The required frequency increased with increased levels of Br-2 injection through the burner. The impact of cleaning suggests that bromine species may be accumulating on the glass and subsequently heterogeneously oxidizing elemental mercury. Difficulties in recovering total mercury are not seen when using chlorine as the oxidant. The determination of elemental mercury in the presence of bromine and SO2 yielded results that further suggest that mercury may be heterogeneously oxidized on the glass walls of the impingers and chiller. The presence of SO2, whether added through the burner or directly to the KCl impinger, decreased the apparent extent of oxidation of elemental mercury. This decrease may be due to the adsorption of SO2 and possibly SO3 on the glass surfaces, thereby preventing the adsorption of elemental mercury and bromine species and subsequent heterogeneous oxidation of elemental mercury.