A technique is developed for the rapid and precise measurement of the secondary electron emission properties of certain dielectric surfaces. The dielectric surface is bombarded by primary electrons having energies which produce a secondary emission ratio greater than unity. This establishes the surface potential at a known value. With the known potential difference between the dielectric surface and primary electron source, the energies of the primary electrons are automatically determined for the first instant of surface bombardment. The net current to the dielectric surface at any moment is measured by using a cathode‐ray oscillograph to observe the transient current to a metal plate which backs the dielectric. The method has been used to study metallic surfaces and has yielded results which agree very closely with those obtained using the conventional d.c. method of measurement.