A simple time‐of‐flight method has been employed as a means of measuring cyclotron beam energy. Through use of a movable and a fixed stilbene scintillation detector, a phase delay measured in terms of the cyclotron frequency is introduced by the flight time of the beam particles. Results good to 2 percent in energy have been obtained. These have less precision than the direct errors of the method, largely because of cyclotron instabilities.