The energies of silver (Ag) atoms in Ag nanoparticles supported on different cerium and magnesium oxide surfaces, determined from previous calorimetric measurements of metal adsorption energies, were analyzed with respect to particle size. Their stability was found to increase with particle size below 5000 atoms per particle. Silver nanoparticles of any given size below 1000 atoms had much higher stability (30 to 70 kilojoules per mole of silver atoms) on reduced CeO(2)(111) than on MgO(100). This effect is the result of the very large adhesion energy (similar to 2.3 joules per square meter) of Ag nanoparticles to reduced CeO(2)(111), which we found to be a result of strong bonding to both defects and CeO(2)(111) terraces, apparently localized by lattice strain. These results explain the unusual sinter resistance of late transition metal catalysts when supported on ceria.