Iridium was supported on TiO2 and other metal oxides by the deposition precipitation method and was examined for the oxidation of CO and of H-2. Iridium supported on TiO2 was active at temperatures below room temperature for CO oxidation and was much more active than Ir/SnO2, Ir/Al2O3, and Ir/Fe2O3. TEM observations showed that Ir was spread over the TiO2 surface as a thin layer, 2 nm thick, the structure of which was completely different from those of other noble metal catalysts.