Phase constituents and transformations of plasma-sprayed thermal barrier coatings (TBCs) with CeO2-stabilized ZrO2 (CSZ; 16-26 wt% CeO2) have been investigated using X-ray diffractornetry (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The as-coated CSZ coatings with 16 and 18 wt% CeO2 consisted only of the nonequilibrium tetragonal (t') phase. A mixture of the t' and the nonequilibrium cubic (c') phases was observed for the as-coated CSZ coatings containing 20-26 wt% CeO2. During 65 min cyclic oxidation at 1135degreesC (45 min hold time) in air, the t' or the mixture of the t' and the c' phases decomposed to the equilibrium tetragonal (t) and the equilibrium cubic (c) phases. Some of the t phase transformed to the monoclinic (m) phase on cooling. More m phase was observed to develop in the CSZ coating containing 16 wt% CeO2 than in the other coatings. More m phase was observed on the top surface than on the bottom surface of the CSZ coating. Spalling of the plasma-sprayed CSZ coating during thermal cycling occurred after 230 cycles for the CSZ coating containing 16 wt% CeO2, whereas the lifetime of the CSZ coatings with 18-26 wt% CeO2 ranged between 320 and 340 cycles.