Ultrafine systems of zinc oxide and cerium oxide for use as ultraviolet filter were synthesized by a non-alkoxide sol-gel process at different temperatures, to obtain solid materials (40 and 70 degrees C), that were characterized by X-ray diffraction, scanning electronmicroscopy, UV-vis reflectance. Their catalytic and photocatalytic activities were also evaluated. ZnO:CeO2 systems present higher UV absorption and transparency in the visible region. The photocatalytic activity of ZnO:CeO2 systems for the oxidation of organic materials is much smaller than that of titania, ceria and zinc oxide, suggesting that ZnO:CeO2 systems are promising candidates for use as optical materials in UV-filters. (C) 2009 Elsevier B.V. All rights reserved.