A systematic investigation of the catalytic oxidation of 1,2-dichlorobenzene (o-DCB) was conducted over a series of supported vanadia/alumina catalysts. The reaction was found to be first-order in o-DCB and zero-order in O-2 under excess oxygen conditions. Deactivation studies conducted with a 5.6% V2O5/Al2O3 catalyst at 773 K indicated a 15% loss in activity after 75 h on-stream. In situ FTIR studies suggest that the benzene ring remains intact during the adsorption of o-DCB, while no surface species containing C-CI bonds were detected. Thus, it is suggested that chlorine abstraction is the first step in the reaction. Several partial oxidation products, namely phenolates, maleates and carboxylates were observed on the catalyst surface under reaction conditions. All of these species with the exception of the maleates can react with gas phase oxygen.