The chemistry between NOx species adsorbed on La2O3 and CH4 was probed by temperature-programmed reaction (TPR) as well as in situ DRIFTS. During NO reduction by CH4 in the presence of O-2, NO3- does not appear to activate CH4, thus either an adsorbed O species or an NO2- species is more likely to activate CH4. In the absence of O-2, a different reaction pathway occurs and NO-or (N2O2)(2-) species adsorbed on oxygen vacancy sites seem to be active intermediates, and during NO reduction with CH4 unidentate NO3-, which desorbs at high temperature, behaves as a spectator species and is not directly involved in the catalytic sequence. Because reaction products such as CO2 or H2O as well as adsorbed oxygen cannot be effectively removed from the surface at lower temperatures, steady-state catalytic reactions can only be achieved at temperatures above 800 K, even though formation of N-2 and N2O from NO was observed at much lower temperature during the TPR experiments.