X-ray diffraction techniques have proved invaluable in the characterization of infrared materials, particularly those prepared by thin film deposition techniques such as molecular beam epitaxy, MBE. The techniques are sufficiently sensitive and rapid to provide the information feedback required for efficient optimization of the growth process. They are nondestructive and permit the correlation with results on the same sample obtained by other characterization techniques such as those being described at this Symposium. Depending on the development status of the growth technology, the information to be acquired includes presence of twinning, quality, and type of epitaxial orientation, strains, and compositional variations. A critical issue in the application of these materials in detector arrays is the question of uniformity control, both laterally and in depth. The techniques to be described include not only modern x-ray topographic and multiple crystal diffractometric techniques but particularly for the early stages of growth process development, classical photographic ones such as the oscillation and Weissenberg methods. Examples of these various aspects are presented with emphasis placed on the characterization involved in MBE growth of HgCdTe films.