The sintering behaviour of Pd or Pt loaded ceria-zirconia solid solutions of nominal composition Ce0.50Zr0.50O2 and Ce0.68Zr0.32O2 was studied under oxidising conditions. Calcination treatments were carried out under controlled oxidising atmosphere for periods of up to 96 h. Powder X-ray diffraction and BET nitrogen adsorption-desorption derived surface area data are reported for the bare materials and for those loaded with low (<1% w/w) amounts of the noble metals, palladium and platinum. Phase demixing was observed as sintering progressed for both of the compositions studied with some differences in behaviour observed between the noble metal free and noble metal loaded catalysts. The results are discussed from a thermodynamic viewpoint, which allows to distinguish the behaviour of the two compositions during the demixing process.