Shaped Co spinel catalyst 5 x 5 mm (M. Inger et al., 2011) was used for decomp. of N2O in industrial tail gas from HNO3 prodn. (N2O content 300-1500 ppm, temp. 320-425 degrees C) for 1735 h. The long term results showed quite full conversion of N2O at above 400 degrees C and gas flow velocity below 10000 h(-1). The N2O decompn. was the first order diffusion-controlled reaction.