yAu/SnO2 (y = 1-5 wt%) and 1 wt% Pt- or Pd-doped 3Au/SnO2 catalysts were prepared by the co-precipitation method. It is observed that the 3Au/SnO2 catalyst showed the best performance (T-100% = 166 degrees C). The pretreatment of 3Au/SnO2 in CO obviously decreased the catalytic activity due to the reduction of oxidized gold species to metallic Au-0. Pd- or Pt-doping to 3Au/SnO2 brought about a significant enhancement in performance, with the T-100% value being 74 and 93 degrees C, respectively. It is concluded that the oxidized gold species were more active than metallic Au-0 and the remarkable improvement in catalytic activity due to Pd or Pt doping was associated with the presence of strong interaction of Pd or Pt with Au.