Gold over zirconia and sulfated zirconia catalysts were tested in the water-gas shift (WGS) reaction at temperatures between 423 and 453 K. Samples were characterized by N-2 adsorption analysis, XRD, TPO, TG-DTA and pulse-flow CO chemisorption. A very good linear relationship between catalytic activity and dispersion determinated by chemisorption has been evidenced. Sulfated catalysts showed higher activities than samples over plain zirconia. SO4- do not behave as promoters of the gold active phase, but they yield a larger specific surface area of the zirconia, thus favouring a better dispersion of gold nanoparticles on the support. CO amount at the reactor outlet has been checked and will be discussed. (C) 2009 Elsevier B.V. All rights reserved.