The present state of grating spectroscopy is reviewed with special emphasis on the far ir. The review includes the discussion of the properties of diffraction gratings, the intensity distribution among different orders of echelette gratings, Wood anomalies, ir and submillimeterwave filters, detectors, grating spectrometers with thermal sources, rules for the construction of far ir and submillimeterwave grating spectrometers, diffraction at the monochromator slits, comparative performance of interferometers and grating spectrometers, and spectroscopy of far ir laser emissions. Extensive references are presented.