Changes in the potentials of electrodes with tantalum(V) oxide layers of ≈ 2 microns thickness under lighting with middle pressure mercury lamp were followed up in test experiments. Electrodes of two types were under investigation: doped by W and doped by Fe. Tantalum oxide layers were obtained by thermal oxide formation on metallic tantalum. W and Fe were contained in the form of surface oxide admixtures. Both types of electrodes revealed photo-potentials which were developed towards the negative region. Such behavior indicated on n-type conductivity of the samples. The effect was observed up to long-wavelength cutoff of UV-range. The greatest values of photo-potential (≈ 270 mV) were observed for the electrodes doped by W under light irradiation of the energy range corresponding to intrinsic absorption of Ta2O5. Photo-potentials developed by Fe-doped electrodes were lower more than by order of magnitude. Refs 18. Figs 4.