A series of catalysts prepared with activated carbons, doped with some vanadium compounds including the ashes of a petroleum coke, have shown considerable activity in the reduction of NO in the presence of ammonia, at relatively low temperatures (100-300 degrees C). The presence of 10% (v/v) water vapour caused a considerable decrease in activity. The presence of 200 PPMV Of SO2 in the reactant gas mixture did not appear to cause any depletion of the NO reduction efficiency. Higher NO reduction efficiencies were measured for the catalysts prepared using preoxidised supports. (c) 2005 Elsevier B.V. All rights reserved.