The effect of copper metal supported on activated carbon on the catalytic reduction of NO has been studied as a short reaction process. It was observed that the adsorption properties of the activated carbons plated with copper metal slightly decrease with an increasing in the, plating time or amount of copper metal, within the range of well-developed micropores. The results of reduction show that the presence of copper metal on activated carbon remarkably promotes the NO reduction conversion with the time on stream in the presence of oxygen. Rut a marginal decrease in the function of plating time is observed. Meanwhile, the NO conversion is almost constant being about 100% after standing 20 h on stream at 500 degrees C in spite of the absence of oxygen. The effects of plating time, experimental temperature, and oxygen amount in the activated carbons have been discussed concerning the NO-copper and/or NO-carbon catalytic reaction.