A Ce/Zr mixed oxide with a molar ratio of 68/32 was submitted to aging treatments in different environments: one oxidizing, one reducing, and one in which the feedstream was continuously changing between oxidizing and reducing through the stoichiometric composition. The textural evolutions of the differently aged samples have been compared to each other and also to the fresh sample and have been related to the samples＇ activities as three-way catalysts. The activities of the samples have been found to depend not only on the samples＇ final specific surface areas but also an the reducing or oxidizing nature of the aging treatment. Thus, it has been pointed out that an aging feedstream as similar as possible to the actual one in real operation should be used when performing durability studies to arrive at reliable conclusions.