Catalyst reducing the toxic contaminants of exhaust gas of combustion engines. The catalyst, which consists essentially of a ceramic honey comb structure as carrier and a mixture of copper, nickel and manganese oxides as catalytically active ingredients, has an intermediary layer of aluminum oxide applied to the honey comb carrier.The catalyst is produced by heating the honey comb carrier to 300.degree. - 400.degree.C; by introducing the hot carrier into a concentrated solution of an aluminum salt of a volatile acid for 15 - 60 minutes; by blowing out the carrier and drying it at room temperature; by heating the dry carrier within 1 to 4 hours to 350.degree. - 450.degree.C and then calcining it for 2 to 6 hours to 500.degree. - 700.degree.C with the resultant formation of an intermediary layer of aluminum oxide on the honey comb carrier; by heating the carrier to 300.degree. - 400.degree.C; by dipping the hot carrier in a hot concentrated aqueous solution of catalytically active copper, nickel and manganese salts of volatile acids and allowing it to remain therein for 15 - 60 minutes; by blowing out the carrier and drying it for 1 - 4 hours at 350.degree. - 450.degree.C; and by calcining it for 5 - 20 hours at 700.degree. - 1000.degree.C.