The structure and reactivity of Rh films supported on the surface of a CeO2 single crystal were studied using Auger electron spectroscopy (AES) and temperature-programmed desorption (TPD). Rhodium films deposited from the vapor phase were found to grow via the nucleation of three-dimensional particles at a sample temperature of 300 K. Annealing of the Rh films resulted in further agglomeration of the metal layer. Carbon monoxide TPD spectra obtained from Rh supported on oxygen-annealed CeO2(111) and CeO2(100) substrates were similar to those obtained from the low-index planes of Rh single crystals, with the exception that a small fraction of the CO (ca. 2%) was oxidized to CO2. In contrast, a new high-temperature CO desorption state was observed in the TPD spectra obtained from Rh supported on partially reduced CeO2 surfaces.