Methods for surface metrology have advanced significantly in the last few years, driven largely by the metrology needs for advanced lithographic processes. In addition, tools exist to predict the scatter from low roughness mirrors and fine-pitch gratings such as are used for ultraviolet to X-ray optical systems. On these pages applies recently developed metrology techniques to the specific problem of determining the groove structure, efficiency, and scattering of diffraction gratings well enough to reliably predict performance. Metrology devices used include an atomic force microscope, a contact profilometer, a late-model optical microinterferometer, a highly automated spectrograph, a fully automated ultraviolet spectrographic tester, and a beamline’s monochromator. Examples of shallow (far-UV, high dispersion) and deep (IR echelle) gratings are presented, along with some conclusions of which metrology techniques are applicable for which types of diffraction grating.