This work aims to show a selection process for natural crystals that considers the major characteristics and performance as gratings for neutron monochromators using the neutron diffraction technique. A total of 19 crystals have been selected and classified regarding their adequacy for use as neutron diffraction devices. Applying special criteria, method and the rocking curve technique, the measurements have been performed and the theoretically available values compared with the experimental results, obtained directly from a neutron diffractometer in operation at the IEA-R1 (5 MW) nuclear research reactor. The choice for natural crystals, expanding the operational range of the neutron diffraction instruments, is related with the purpose of getting monochromatic neutron sources suitable for the applications. The neutron has proved to be the most powerful microscopic testing particle in condensed matter studies and in many other areas of application. ©1998 American Institute of Physics.