A diffraction grating mounted in the focal region of a modified scanning electron microscope has been used to produce far-infrared Smith–Purcell radiation. The electron beam radius, voltage, and current ranges were 3–27 μm, 27–40 kV, and 10–140 μA, respectively. The micron scale of the electron beam was well matched to the evanescent surface waves of the grating. The measured wavelength range extended from 288 to 803 μm, and both the wavelengths and the intensities observed were in accord with expectations based on theory. The details of the experiment and a summary of the results will be discussed.