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Temperature-programmed isotopic exchange of ¹⁸O₂ with ¹⁶O of several oxides was carried out in the 200−900 °C temperature range. The oxides can be ranked according to their maximal rates of exchange obtained at the following temperatures:  CeO₂, 410 °C ≫ CeO₂-Al₂O₃, 480 °C ≈ MgO, 490 °C > ZrO₂, 530 °C ≫ γ-Al₂O₃, 620 °C ≫ SiO₂, 850 °C. Except on CeO₂ and on CeO₂-Al₂O₃ a simple exchange yielding initially ¹⁸O¹⁶O can be observed. With ceria containing oxides, the reaction occurs in part via a multiple exchange mechanism yielding initially ¹⁶O₂ which is indicative of the presence of binuclear species (O₂, O₂^-, or O₂^2-) at the ceria surface. Chlorine-free rhodium catalysts supported on these oxides were prepared with metal dispersions between 32 and 89%. The presence of rhodium accelerates considerably the oxygen exchange with the support:  the maximal rates of the exchange can be …