Dispersing La2O3 on delta- or gamma-Al2O3 significantly enhances the rate of NO reduction by CH4 in 1% O-2, compared to unsupported La2O3. Typically, no bend-over in activity occurs between 500 degrees and 700 degrees C, and the rate at 700 degrees C is 60% higher than that with a Co/ZSM-5 catalyst. The final activity was dependent upon the La2O3 precursor used, the pretreatment, and the La2O3 loading. The most active family of catalysts consisted of La2O3 on gamma-Al2O3 prepared with lanthanum acetate and calcined at 750 degrees C for 10 h. A maximum in rate (mol/s/g) and specific activity (mol/s/m(2)) occurred between the addition of one and two theoretical monolayers of La2O3 on the gamma-Al2O3 surface. The best catalyst, 40% La2O3/gamma-Al2O3, had a turnover frequency at 700 degrees C of 0.05 s(-1), based on NO chemisorption at 25 degrees C, which was 15 times higher than that for Co/ZSM-5. These La2O3/Al2O3 catalysts exhibited stable activity under high conversion conditions as well as high CH4 selectivity (CH4 + NO vs. CH4 + O-2) The addition of Sr to a 20% La2O3/gamma-Al2O3 Sample increased activity, and a maximum rate enhancement of 45% was obtained at a SrO loading of 5%. In contrast, addition of SO4= to the latter Sr-promoted La2O3/Al2O3 catalyst decreased activity although sulfate increased the activity of Sr-promoted La2O3. Dispersing La2O3 on SiO2 produced catalysts with extremely low specific activities, and rates were even lower than with pure La2O3. This is presumably due to water sensitivity and silicate formation. The La2O3/Al2O3 catalysts are anticipated to show sufficient hydrothermal stability to allow their use in certain high-temperature applications.