The degradation of 100 mg/L phenol solution under ultraviolet (UV) in the presence of TiO2 and in the absence of it was analyzed with gas chromatography/mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). After 12h of degradation, the products under the two conditions were both derivatized by MSTFA and TMIS, and then analyzed by GC-MS. The results show the main intermediates are the same. They are hydroquinone, resorcinol, catechol, 1,2,3-benzenetriol, (E)-2-butenedioic acid, 2-hydroxy-propaldehyde, glycerol, 3-hydroxypropyl acid, and hydroxy-acetic acid. The chromatogram given by HPLC indicates that the presence of TiO2 is not in favor of the degradation when the concentration of phenol is 100 mg/L; its catalysis becomes evident when the concentration gets lower. Based on the intermediates, it can be proved that besides (OH)-O-., H-. is also an important active free radical in the degradation. (c) 2006 Elsevier B.V. All rights reserved.