Gold-copper alloy catalysts were prepared by impregnation of TiO2 (anatase) support with mixed chloride precursors and tested in the gas-phase epoxidation of propene. The bimetallic systems contained different Au-Cu molar ratios and a total metal content of 4 wt.%. The corresponding monometallic AU/TiO2 and Cu/TiO2 catalysts were also prepared for comparison. X-ray diffraction, XPS and transmission electron microscopy studies indicated that alloying was achieved. The copper content in the catalyst seemed to have a strong influence on the dispersion and catalytic properties of the metal particles. In particular, the greater the Cu content in the alloy, the smaller the metal particle. These changes also contributed to an increase in activity and selectivity to propene oxide. The sample with a Cu/Au ratio of 3/1 showed the best catalytic behaviour. Moreover, the catalytic activity of the samples can be correlated with the results obtained by TPR. (C) 2007 Elsevier B.V. All rights reserved.