Au/CeLaOx mixed oxide catalysts containing 0.6-1.0 wt% Au were prepared by co-precipitation with Na2CO3. BET surface areas ranged from 15 to 45 m(2)/g depending on aging time (precipitation time) and calcination conditions. The differences in the activity of the catalysts for preferential oxidation (PROX) of CO are ascribed to the differences in the metal loading, Ce/La ratio and support crystallinity, chloride content, and the resultant effect on the reduction properties of the catalysts. The catalysts did not require activation in H-2 prior to reaction. The temperature at which the catalysts exhibit significant activity correlates with the temperature of reduction, indicating that reduction of the metal and support is important for high activity.