In the temperature range 200-550 degrees C, an investigation has been made of the selective reduction of nitrogen oxide by methane in the presence of oxygen on polycomponent oxide compositions consisting of binary mechanical mixtures of industrial catalysts with a different mass ratio of components: MK1 (1, 2, 3) - nickel-chromium oxide and NTK-10-1; MK2 (1, 2, 3) - STK and NTK-10-1. It has been established that the degree of conversion of NO to N-2 on MK1 and MK2 in gas mixtures not containing oxygen amounts to 90-99% at 200-400 degrees C; when 4-5% oxygen is added to the gas mixture, the degree of conversion of NO on these catalytic compositions amounts to 30-99% in the temperature range 350-500 degrees C. It has been established for the first time that catalytic systems MK1 (2, 3) exhibit synergistic properties during the reduction of nitrogen oxide by methane both in the presence of oxygen and without it, whereas on the MK2 (3) system synergism is found only in a gas mixture not containing oxygen.