A study has been made of the selective reduction of nitrogen oxide by propane in the temperature range 200-550 degrees C in the presence of oxygen on polycomponent oxide composites consisting of binary mechanical mixtures of industrial catalysts: MK1 (1, 2, 3) - nickel-chromium oxide and NTK-10-1; MK2 (1, 2, 3) - STK and NTK-10-1. Synergism has been found for catalytic systems MK1, (1, 2, 3) and MK2 (1, 2, 3), manifested by their higher activity in the reduction of nitrogen oxide by propane by comparison with the individual catalysts contained in these composites. The activity of catalytic systems MK1 (1, 2, 3) and MK2 (1, 2, 3) in the oxidation of propane by oxygen has been compared. It has been established that the order of activity for each series of catalysts studied in the reduction of NO by propane and the oxidation of propane by oxygen coincides in the two reactions. This experimental fact indicates the relationship between the conversions of nitrogen oxide and propane, and it is assumed that, in the presence of oxygen, the reducing agents in the selective reduction of NO are intermediates formed by the oxidation of propane.