Activity of 0.5-10% Au/Fe2O3 or /TiO2 or /Al2O3 catalysts prepd. by impregnation (with aq. HAuCl4), co-pptn., or deposition-pptn., was studied in oxidn. of 3% CO with 6% O-2 in He in a flow reactor at -80 to 500 degrees C. The conversion/catalyst activity fell in the descending support order: Fe2O3 > TiO2 > Al2O3. Alkalis (10% KOH) activated low-activity catalysts and also reduced the reaction temp. by as much as 200 degrees C. The copptd. and the deposited (with urea as additive) catalysts were superior (Au crystallites < 5 nm) to the impregnated catalysts. Pptn. agents affected the conversion deg. in the descending order: KOH > Na2CO3 (NaBH) > Na2CO3 > NH3.