The kinetics of photocatalytic (TiO2/UV) degradation of 2-chlorophenol (2-CP), characterization of intermediates and induction of biodegradability in treated chlorophenol solutions is reported. Approximately 95% of the 2-CP is removed in approximately 2 h at pH 5 and 0.2 g TiO2 l(-1) when the 2-CP concentration is less than or equal to 100 mgl(-1) ; the pseudo-first-order rate constant (k) is estimated to be 0.0183 min(-1). GC-MS analyses detected phenol, catechol, hydroxyhydroquinone (HHQ), and chlorohydroquinone (CHQ) intermediates during the short irradiation time (< 1 h); however two other higher carbon intermediates 2-hydroxy-benzaidehyde (HB) and [1.1'-biphenyl]-2,2'-diol (BPD) are found as major intermediates over longer irradiation times. The biochemical oxygen demand (BOD) of treated 2-CP solutions improved substantially. A tentative mechanistic pathway to explain formation of higher carbon intermediates is presented. (C) 2003 Elsevier B.V. All rights reserved.