First-order kinetics was found for the photocatalytic oxidation of catechol on TiO2. Kinetic constants calculated from the Langmuir-Hinshelwood equation are: k=2.03x10(-8) mol dm(-3) s(-1); K-ads=1.63x10(4) dm(3) mol(-1). Full catechol mineralization is a multistep reaction, 1,2,4-benzenetriol and glycol are the main intermediates.