Abstract The photocatalytical reduction of Cr(VI) in aqueous suspensions of ZnO under uv-illumination is studied. The amount of Cr(VI) photoreduced at different irradiation times, initial Cr(VI) concentrations, pH and temperatures have been determined. Different ZnO—doped samples have been used in order to improve the yield of the Cr(VI) photoreduction. Finally, some experiments under sunlight have been performed. The results obtained in the present work show that ZnO can be used as efficient catalyst for the photoreduction of Cr (VI) in aqueous solutions even under sunlight exposure.