In this paper, the photocatalytic degradation of terephthalic acid (TPA) using titania and zinc oxide nanoparticles was investigated. UV-Vis spectrophotometer and high performance liquid chromatography (HPLC) were used to study the TPA degradation. The effect of influential parameters such as initial pH, catalyst loading, initial TPA concentration and H2O2 were studied. It was found that the photocatalytic degradation of TPA obeyed the pseudo-first order kinetic reaction in the presence of both photocatalysts. The aliphatic carboxylic acids such as oxalic, formic, maleic, acetic and fumaric acids were detected by HPLC during the degradation of TPA. The results show that TiO2 and ZnO photocatalysts can be employed as an effective photocatalyst for the elimination of TPA from wastewater but in optimized conditions zinc oxide was a more efficient catalyst than TiO2. (C) 2009 Elsevier B.V. All rights reserved.