Au/Al2O3 center dot xH(2)O and Au/TiO2/Al2O3 center dot xH(2)O (x = 0-3) catalysts were prepared by assembling gold nanoparticles on neat and TiO2-modified Al2O3, AlOOH, and Al(OH)(3) supports, and their catalytic activity in CO oxidation was tested either as synthesized or after on-line pretreatment in O-2-He at 500 degrees C. A promotional effect of TiO2 on the activity of gold catalysts was observed upon 500 degrees C-pretreatment. The catalyst stability as a function of time on stream was tested in the absence or presence of H-2, and physiochemical characterization applying BET, ICP-OES, XRD, TEM, and Al-27 MAS NMR was conducted.