A deposition-precipitation method was used for preparing TiO2, TiOxNy and TiN supported gold catalysts. The dispersion and average size of the gold particles are dependent of the nature of the support, probably of their acid-base properties. Transmission electron microscopy (TEM) observations reveal an homogeneous distribution of gold particles lower than 4 nm on TiO2. However. on TiN, a wide distribution of gold particle diameters ranging from 3 nm to 1 mum is detected. On TiOxNy support, where both TiO2 (anatase) and TiN phases are present, gold is selectively deposited on the oxide. On the other hand, only the fresh Au/TiO2 sample shows any room temperature activity to the CO oxidation, according with the homogeneous distribution and lower average size of their gold particles. (C) 2003 Elsevier Science B.V. All rights reserved.