Electron metallography in its various forms has now reached the point where it can be used to characterize nearly all of the microstructural features which occur in materials including grain and subgrain size and shape; dislocation density and configuration; precipitate size, shape, and coherency strain; antiphase domains in ordering alloys; and magnetic structure in ferromagnetic alloys, as well as chemical composition changes on a very fine scale. Transmission electron microscopy (TEM) provides the most complete information about internal structures and is especially effective when used in conjunction with scanning microscopy of the same specimen. Development of high voltage instruments capable of operating at 1 mV or more has broadened the scope of application of electron metallography particularly because of the ability to penetrate significantly thicker specimens than with conventional 100 kV instruments. Other important characteristics of high voltage electron metallography (HVEM) such as greater accuracy in selected area diffraction, reduced chromatic aberration of thick specimens, and a unique critical voltage effect are discussed. Typical applications such as studies of recrystallization, deformation, recovery, precipitation, and ordering are described, as well as quantitative three-dimensional (stereo) analysis of dislocation distributions and electron radiation damage.