A theoretical investigation of the photovoltage produced in insulated CdS‐type crystals excited by strongly absorbed radiation has been carried out, taking into account trapped electrons and trapped holes in addition to free electrons. Expressions for the photovoltage dependence on intensity for isolated crystals have been obtained over a wide range of excitation levels. A plot of typical density profiles for the free electrons, trapped electrons, and trapped holes as functions of position is given. It is shown that the results can readily be extended to nonisolated crystals.