An Al(2)O(3)-supported Fe(2)O(3) Catalyst Was used for decompn. of N(2)O in a pilot plant for catalytic oxidn. of NH(3) to NO at 860 or 900 degrees C, 3.5 or 4.8 atm. and reactor load 5.5 or 12.0 t N/m(2)d, resp. The initial N(2)O concn. was 1100-1300 ppm. The catalyst was then used in 2 Polish plants for manufg. HNO(3) (Anwil Wloclawek and ZAK Kedzierzyn-Kozle). The use resulted in a substantial decrease in the N(2)O emission (by about 80% and 91%, resp.). No remarkable changes in the NO yield from the reactors were obsd.