Alumina supported Pt-Au bimetallic catalysts, in which Au was deposited onto Pt by reduction of AuCL4- with adsorbed hydrogen, were studied using hydrogen TPD and X-ray diffraction. Their catalytic behavior was tested in methylcyclopentane reaction. The gold inhibits the hydrogen adsorption indicating that gold atoms are deposited on platinum sites. In methylcyclopentane reaction, the catalysts containing the largest amounts of Au, promoted the formation of dehydrogenation products although in conversions very low. However, the environmental conditions or oxidation treatments irreversibly affect the catalytic behavior in these systems, suggesting a rearrangement of the metallic sites created by the redox reaction. This rearrangement effect was investigated by X-ray diffraction and by high resolution electron microscopy (HREM) studies.