Continuous photocatalytic oxidation of aromatic contaminants at 10 ppm or above generally leads to apparent catalyst deactivation. This deactivation has been attributed to the accumulation of recalcitrant intermediate species on the catalyst surface. In the present study, two variations of a simple kinetic model for the transient photocatalytic oxidation of an aromatic contaminant are considered. Modeling results are compared to our experimental data for the gas-phase photocatalytic oxidation of benzene, toluene, and m-xylene. A kinetic model using a single type of adsorption site is unable to replicate the experimental results. A second model, using a Two-Site arrangement, was developed based upon studies addressing multi-site binding of alcohols and other oxygenated hydrocarbons. This Two-Site kinetic model was able to produce results consistent with experimental data. (C) 2002 Published by Elsevier Science B.V.