With in situ IR, two different CO adsorption bands weredetected on various chemical state gold catalysts. One band isattributed to the linear CO on an oxidized gold catalyst(2100 cm-1),the other one is ascribed to the bridged CO on metallic gold (2085cm-1). CO pulse reaction showed that Au/Fe2O3 catalyst had aroom-temperature activity even in the presence of moisture. Theproduced CO2 was detained and more easily desorbed from supportedgold catalyst than support oxide. TPD-IDT results indicated thatthe O2- superoxide ions are the possible active oxygen species.