The use of high-energy electron beams in industrial processing has been the subject of considerable publicity in the last two or three years. Radiologists are always interested in the application of any type of ionizing radiation and, since the development of x-ray equipment for medical purposes often reflects the design of equipment for industrial uses, it seems logical to assume that radiologists as a group have been interested in this development. The purpose of the present paper is to review some of the history of non-medical uses of electron beams, to indicate some of the current industrial applications, and to point out some future possibilities. In most devices electrons are contained within the device itself. Electron-beam sources are different in that the electrons are brought out of the device or generating source. Like most technical developments, the use of electron beams is not new. Prior to the last few years, however, they were limited to scientific studies rather than to any large-scale practical application. Lenard, in 1894, described a tube from which it was possible to bring out the electrons through an aluminum foil window. Although his tube operated at low voltages, the air in front of the window showed luminosity for a distance of 5 cm. Fluorescent materials became luminescent at distances as great as 6 to 8 cm. from the window. Des Coudres devised a cathode-ray tube in 1897 and tubes of this type were described by Pauli in 1910 and again in 1920. In 1925 Kruger and Utesch published an account of a hot cathode, high-vacuum tube for producing an external beam. All these early tubes probably worked at less than 100 kv. In 1926, Coolidge described a tube for operation at voltages up to 250,000 volts. With this he studied the possible changes in the color of diamonds, the changes in fused quartz and sodium chloride crystals, changes in electrical insulators, electron radiographs of delicate tissues, chemical effects on aqueous solutions, the action on bacteria, plant, and animal tissues, and the doses required to destroy fruit flies, snails, and cockroaches. Tissue effects were also studied in a long series of experiments in which small areas of rabbits' ears were exposed. At about the time that Coolidge was conducting his experiments, Brasch and Lange in Germany were seeking a very high-voltage source for atomic research. They strung a long antenna between two peaks on Mt. Genoroso, in that region of the Alps where thunderstorms and lightning discharges were common, and were able to obtain and measure short time impulses as high as 20,000,000 volts. They then returned to Berlin and set out to develop an electron tube for use in their atomic studies. Before this could be finished, however, Cockcroft and Walton in 1932 completed their work and “smashed the atom,” using 200,000-volt protons.