The photocatalytic degradation of diuron, which is one of phenylurea herbicides, was carried out in the presence of platinized TiO(2) photocatalyst. Platinization was found to increase the rate of diuron degradation. When 0.2wt.% of platinum was deposited onto the surface of TiO(2), an initial diuron concentration of 10 mg L(-1) was completely degraded after 20 min. Furthermore, the first-order rate constant for diuron degradation by Pt-TiO(2) was ca. 4 times higher than P-25 TiO(2). In addition, the photocatalytic activity of Pt-TiO(2) was appeared under visible light. The decrease of TOC as a result of mineralization of diuron was observed during the photocatalytic process. The degree of diuron mineralization was about 97% under UV irradiation after 8h. The formations of chloride, nitrate and ammonium ions as end-products were observed during the photocatalytic system. The decomposition of diuron gave four kinds of intermediate products. The degradation mechanism of diuron was proposed on the base of the evidence of the identified intermediates. Based on these results, the photocatalytic reaction by Pt-TiO(2) could be useful technology for the treatment of wastewater containing diuron.