This paper reports a study on the influence of calcination temperature on the catalytic behavior of the Au/iron oxide systems in the water-gas shift reaction. The catalytic activity has been found to be strongly dependent on the catalyst pretreatment, decreasing on increasing the calcination temperature. Detailed characterization of the uncalcined and the calcined sample at different temperatures, employing BET analysis, XRD, H-2-TPR, HRTEM and XPS, has shown that the catalytic behavior is related to the gold state and/or the particle size and the properties and structure of iron oxide support. Both the oxidation state and dispersion of gold and the phase transition and its crystallinity and reductive property of the support exert great influence on the catalytic performance of the gold/metal oxide. The wave of the activity within the middle reaction temperature range (i.e. 523-623 K) could be attributed to the difference of the operating temperatures belonging to the gold species and the active magnetite phase. (C) 2003 Elsevier B.V. All rights reserved.