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The reduction behaviour of Ce x Zr1−x O2 and Pt or Pd supported on Ce x Zr1−x O2 was investigated by means of XANES measured at the Ce LIII edge and magnetic susceptibility measurements. Both techniques agree quite closely for the materials studied. The presence of a noble metal greatly improves the reduction of the Ce x Zr1−x O2 support at low temperatures. The reoxidation that occurred after evacuation of the reduced solids and heating to 500°C suggests that it is linked to a reversible surface reduction process of the sample.