This paper describes a study of ion migration in polycrystalline rutile (TiO2) films making use of a new MOOS device of the form metal electrode/TiO2/SiO2/Si. Ion migration in rutile films has been monitored through the use of temperature-bias treatments, followed by capacitance-vs-dc bias (C-V) measurements. Field-induced ion migration is induced at considerably lower temperatures in rutile than in SiO2. Large horizontal negative shifts in the C-V curve occur following biasing at elevated temperatures when the metal electrode has been positively biased. The temperature dependence of these shifts, and therfore, the ionic surface-charge density in rutile films, appears to obey an Arrhenius-type equation, with an activation energy of 0.46 eV. The relaxation time for these shifts is of the order of 17 min at 90 °C. The ions involved in these shifts may arise as a result of field-enhanced production of anion vacancies and mobile Ti+3 ions, or of introduction of protons from chemisorbed water, or of the presence of predominantly alkali metal-type ions.