Abstract: A method of removing nitrogen oxides (NO.sub.x) from exhaust gas mixtures is described. The removal of NO.sub.x from exhaust gas mixtures is accomplished by exposing the exhaust gas mixture, in a manner that does not substantially impede the gas flow, to a ceramic material containing from about 75% to about 95% by weight silicon carbide and from about 0.3% to about 10.0% silica. A reduction of at least 85% of NO.sub.x from the mixture is to be expected and reductions up to 95 to 100% are attainable. Ceramic mixtures containing silicon nitride in amounts between about 10% and about 30% are found to reduce the amount of NO.sub.x in exhaust gases at temperatures as low as 200.degree. C.