Zinc oxide (ZnO) particles were deposited on a very thin titanium dioxide film by a photocatalytic reaction. The particles were formed in an aqueous solution of 0.10 mol dm(-3) zinc nitrate at 343 K. The particles consisted of crystals with 0.20-1.01 mu m-sized hexagonal columns. A photocurrent was observed in the electrodes containing such ZnO crystals during light irradiation.