The reduction of N 2O to N 2 was carried out by temperature programmed surface reaction (TPSR) from 473 to 873 K in He, He + 3% O 2, He + 0.02% NH 3 and He + 3% O 2 + 0.02% NH 3 on H–FAU supported transition metal catalysts. In the absence of oxygen, the addition of NH 3 considerably shifts the N 2O conversion profile towards lower temperatures. This is particularly true for the Ru– and Rh–FAU which exhibit the onset of N 2O conversion around 500 K. The addition of O 2 inhibits this effect for most of the catalysts and NO formation due to NH 3 oxidation is observed. However Fe–, Ni– and Co–FAU kept the best catalytic behaviour for N 2O reduction to N 2 in the presence of O 2, when NH 3 was added to the feed with respect to the decomposition reaction.