The reduction of Cu(II) ions in aqueous suspensions of ZnO under uv illumination is investigated. The study has been carried out by determining the amount of copper metal deposited onto ZnO particles at different irradiation times, salt concentrations, mass of semiconductor in suspension, light intensities, etc. Some electrochemical measurements have been performed by means of the slurry electrode method. It has been observed that the process takes place with high yields, principally at short times of irradiation where no significant electron-hole recombination is present and the screen effect of the copper deposits on the particles is small. © 1986.