The microstructural evolution of nanocrystalline ceria produced by sol-gel has been analyzed as a function of the calcination temperature employing a novel nondestructive method based on the modeling of the whole X-ray diffraction pattern. The results have been thoroughly verified by transmission electron microscopy. A variation both in the average size and in the distribution of the crystalline domains is evidenced. In addition, information concerning lattice defects can be inferred on a larger scale than that normally accessible by microscopy techniques.