The principle of energy measurement by stopping potential has been extended to high‐energy electrons, using conventional accelerating tubes. Defocusing effects which occur during deceleration are minimized by employing a low energy cylindrical electrostatic analyzer to measure the energy remaining in the beam after deceleration has been almost complete. The width of the line profile obtained by this technique appears to be largely independent of the primary energy of the electrons, the percent resolution thus improving as the primary energy is increased. Resolution up to 20 parts per million at 100 kev is obtainable by this method.