The photocatalyzed degradation conditions of di-n-butyl-ortho-phthalate, a representative endocrine disruptor, in aqueous titanium dioxide (TiO2)-suspended solution were optimized. The effect of various factors, such as photocatalyst dosage, initial substrate concentration, temperature, pH and co-existing organic substance, on the photocatalytic degradation of dibutyl phthalate was investigated. The final mineralization product was carbon dioxide during the degradation of dibutyl phthalate in aqueous solution. The intermediate products were identified by GC-MS technique. On the basis of the detected intermediate species and the calculated frontier electron densities of dibutyl phthalate structure, the photocatalytic degradation reaction pathways were proposed. The photocatalytic degradation treatment for the wastewater including phthalic acid esters is simple, easy handling and low cost. (c) 2006 Elsevier B.V. All rights reserved.