The transient photodischarge process in a photoconductor-dielectric sandwich structure due to pulsed light is analyzed. It is assumed that the light is absorbed at one of the surfaces of the photoconductor layer and its duration is short compared to the transit time of the leading edge of the charge carriers. The theory is developed for one type of trap but can be extended to multiple trap types. Time dependent approximations which give the upper and lower limits of the observable parameters are derived up to the transit time and beyond in some cases. It is shown that the two limits are sufficiently close to each other under a rather wide range of experimental conditions so that important transport properties such as mobility, lifetime, and trapping times can be experimentally determined. Examples of calculated results are given by cases involving one type of trap and two types of traps. © 1971 The American Institute of Physics.