The low temperature activity of Au/Fe2O3 catalysts towards CO oxidation was examined with respect to the temperature of pre-treatment and presence of water. The activity of all the prepared catalysts decreased as a result of a high temperature treatment (HTT) at 400 degrees C. The inclusion of water in the gas stream significantly enhanced the oxidation of CO at room temperature. When tested under water gas shift reaction (WGSR) conditions, significantly higher temperatures were required to convert CO to CO2, thereby excluding the possibility of the WGSR during CO oxidation in the presence of H2O at room temperature. The loss of activity for CO oxidation is attributed to the loss of hydroxyl groups and reduction of Au3+ to metallic gold during HTT. The observations are consistent with the model for hydroxyl promotion of the decomposition of a carbonate intermediate by transformation to less stable bicarbonate.