Mechanistic and kinetic aspects of the catalytic decomposition of N2O over knitted Pt gauze were studied by transient experiments in vacuum using the temporal analysis of products (TAP-2) reactor in the temperature range from 573 to 1073 K. At temperatures above 773 K N2O decomposes resulting in the formation of gas-phase oxygen and nitrogen. Gas-phase oxygen was shown to inhibit N2O decomposition over the gauze for all temperatures studied. The transient responses of N2O as well as products of its decomposition (N-2 and O-2) were simultaneously fitted to different kinetic models. Through model discrimination it was shown that molecular oxygen is formed only via interaction of N2O with adsorbed oxygen atoms, originating from the interaction of N2O with metallic Pt sites, as it was speculatively proposed earlier by Riekert and co-workers [Z. Electrochem. 66 (1962) 735; Ben. Bunsen-Ges. Phys. Chem. 67 (1963) 976; Proc. 3rd Intl. Congr. Catal. 1 (1965) 387]. The formation of molecular oxygen via recombination of two surface oxygen atoms was assumed to be slow under transient vacuum conditions as compared to ambient pressure steady-state conditions, due to a lower coverage by these oxygen species. The reaction scheme was supported by results of oxygen-isotopes experiments. (C) 2004 Elsevier Inc. All rights reserved.