Thermally stimulated depolarization (TSD) currents have been studied for lead monoxide powder after dark- and photo-polarization. Two peaks have been observed at 320 and 370 K in the TSD spectra corresponding to trapping levels at 0.3 and 0.5 eV, respectively. From the time and intensity dependence of these peaks it has been shown that the dark polarization is mainly due to the trapping of carriers at shallow levels located at 0.3 eV whereas the photopolarization arises from the carriers trapped at deeper levels corresponding to the second peak. © 1982.