Low-temperature operation is being applied and contemplated for electronic systems ranging from single-transistor circuits for basic research to VLSI integrated circuits for ultra-fast computers. It is seen as both a means of extracting better performance from present technology and as an important ingredient of the next generation of devices and circuits. This overview is concerned with electronics based on semiconductors; for low temperatures the primary material is Si, although GaAs also has considerable potential, and the primary device is the field-effect transistor in various forms. Reduced temperature operation offers improvements in performance through improvement of materials-related properties such as electronic carrier mobility, thermal conductivity, and electrical conductivity. Substantial improvements in reliability are also expected since degradation mechanisms are thermally activated; however, this could be negated unless problems of thermal expansion mismatch and cycling are overcome. Refrigeration continues to be a central concern; mechanical cycles are still the mainstay and progress is being made in systems applicable to electronics, although further development is needed.