The ceria surface area of a commercial Pt-Rh three-way catalyst was  determined after laboratory hydrothermal aging at 1173-1373 K and after 200 h  on engine bench. It was measured by X-ray diffraction (XRD) line broadening  analysis and by a method based on the exploitation of the hydrogen temperature  programmed reduction (TPR) profiles. In this case, the hydrogen uptakes below  about 900 K include the ceria surface reduction and that of the oxidized noble  metals. They are analyzed and discussed, assuming two possiblities for the  metals oxidation state.  Compared to the fresh catalyst, the TPR profiles are deeply modified by  the aging treatments. The ceria seems to sinter more than alumina, particularly  between 1173 K and 1273 K. After aging at 1273-1373 K, the calculated ceria  surface area is only 15-10 m2g -1 washcoat, which represents 20% of the BET area,  instead of 40% initially. A stabilization treatment at 823 K under reactants leads  to an additional ceria sintering, even for the more aged system. Finally, the  measurements on the engine bench aged catalysts seem to indicate a better  resistance of ceria to sintering in working conditions. The presence of a pollutant  layer, containing phosphorus, zinc and calcium, did not modify the accessible  ceria surface area measured by TPR.