The influence of altervalent cation doping of TiO2 carriers on the chemisorptive and catalytic properties of supported Pt and Rh crystallites has been investigated. It was observed that doping of the carrier with higher valence cations leads to suppression of the H-2 and CO chemisorption capacity of Pt catalysts, while their activity in hydrogenation and oxidation reactions is significantly reduced. The opposite effects were observed in the case of Rh catalysts supported on higher valence doped TiO2. These catalysts were found to possess higher activity in CO and CO2 hydrogenation, in aromatics hydrogenation and in CO and C2H4 oxidation. Their stability characteristics were also found to be superior to those of the undoped Rh/TiO2 catalyst. These effects are believed to originate from an electronic type interaction at the metal-support interface, induced by doping, which results in electron transfer from the support to the metal crystallites.