It is shown that theoretical and practical factors limit the intensity of the image of the electron microscope to so low a value that operation under conditions of optimum resolving power is extremely difficult. A method of overcoming this difficulty by the use of a dynamic image intensifier is proposed and its theoretical performance analysed. It is shown to offer possibilities of achieving a displayed image on a cathode-ray-tube display which contains substantially all the information that can be conveyed in the microscope electron beam.The practical realization of this proposal is described, together with evidence that the theoretical prediction is achieved.