A study of the role of the copper promoter in the iron oxide/chromia high temperature water gas shift reaction is reported and discussed. The rate of reaction using both CuO/Fe₃O₄/Cr₂O₃ and Fe₃O₄/Cr₂O₃ catalysts is zero order in H₂O and first order in CO over a wide range of reactant compositions and reaction pressures. The activation energy for the Fe₃O₄/Cr₂O₃ catalyst is found to be 118 ± 9 kJ mol⁻¹ which is in agreement with previous literature data. The addition of CuO to the Fe₃O₄/Cr₂O₃ catalyst significantly decreases the activation energy to ca. 75–80 kJ mol⁻¹. TPR studies using H₂/He and H₂/CO indicate that the addition of CuO partially stabilises the catalyst with respect to reduction with CO, indicating that one role of CuO as a promoter is to permit the use of higher partial pressures of CO in the reactant gases. Model experiments with CH₃OH/CO mixtures show that the addition of CuO to the Fe₃O₄/Cr₂O₃ catalyst promotes the formation of methyl formate significantly. Based on these findings, the possible role of CuO in the promoted catalyst is discussed.