The present study deals with the photocatalytic degradation of the strobilurin pyraclostrobin in the presence of titanium dioxide (TiO2) as a photocatalyst and UV light irradiation. The obtained results show a complete degradation of pyraclostrobin at pH 6.2, temperature at 20 +/- 1 degrees C and 0.5 g L-1 of catalyst after 60 min irradiation. Photodegradation of pyraclostrobin exhibited pseudo-first-order reaction kinetics. The rate of photodecomposition of pyraclostrobin was measured using high performance liquid chromatography-diode array detector (HPLC-DAD). The effect of solution pH in the 2-10 range was investigated as well as the reaction intermediates formed during degradation. To obtain a better understanding of the mechanistic details of this TiO2-assisted photodegradation of pyraclostrobin with UV-irradiation, the intermediates of the processes were concentrated, separated and identified by the solid-phase extraction (SPE) and liquid chromatography/mass spectrometry (LC-MS/MS) technique. The probable photodegradation pathways were proposed and discussed. The main steps involved: hydroxylation of the aromatic rings (chloro-phenyl, phenyl and pyrazol) followed by the loss of the N-methoxy group, substitution of chloride atom by a hydroxyl group, rupture of the pyrazol and phenyl bond and the scission of the oxygen and pyrazol bond. (C) 2011 Elsevier B.V. All rights reserved.