An exptl. catalyst, based on VIII Group elements, calcined at 900 or 1100 degrees C, was used in a pilot reactor operated at 0.49 MPa, 885-890 degrees C, and fed with (10.7:89.3 v/v) NH3-air 45 m(3)(S.TP)/hr., with N2O 1200-1300 ppm (just beneath Pt-Rh gauze), to decomp. N2O in 70-75% in a bed 56 mm high. NO was not decompd. In 3300 hrs. of work in a com. reactor, the 900 degrees C raschig-shaped catalyst was mech. as resistant as before the test and as active as an identical catalyst operated 200 hrs. in the pilot reactor.