Gold and iron supported on Y-type zeolite for carbon monoxide oxidation have been studied. They were prepared by ion exchange of gold(III) compounds with Y-type zeolite, iron-impregnated Y-type zeolite, or iron-exchanged Y-type zeolite in a chloroauric acid solution. The as-prepared gold/Y sample possessed high activity for carbon monoxide oxidation, but it gradually and irreversibly deactivated during the reaction. The deactivation was attributed to the transformation of some gold ions to gold metal. The activities of as-prepared gold/iron/Y samples were poor when compared with that of gold/Y, but their activities were markedly promoted by a high-temperature reduction treatment at 570 degrees C. This is ascribed to the fact that the reduced gold/iron/Y catalyst could catch and release oxygen at low temperature.