A sampling and analysis procedure is described for determining vapor-phase concentrations of As, Se, Br, I, and Hg in the stack of a coal-fired power plant. The percentages of the total in-stack concentrations for these elements present in the vapor phase are as follows: Br, 98%; Hg, 98%; Se, 59%; As, 0.7-52%; and I, ≥99%. A lower limit of 99% ws obtained for Cl. The vapor-phase concentration of As appears to be dependent upon the in-stack or filter mass loading. This indicates that a vaporization-condensation mechanism may control the vapor-phase concentrations of As. The results for Se indicate that the efficiency of the electrostatic precipitator affects particle vapor-phase fractionation. The results obtained in this study are compared with previous mass balance calculations.