The activity of Pt supported on gamma-Al2O3 towards HNCO oxidation and reduction of NO by HNCO under oxygen excess is examined under transient conditions (temperature ramps between 100 and 500 degrees C). Formation of N-2, N2O, NO, and NO2 is observed. Isotope labelled (NO)-N-15 is used to show the scrambling of nitrogens in N-2 ((NN)-N-14-N-15) and N2O ((NNO)-N-14-N-15). Adsorbed species on the surface are characterised by in-situ FTIR spectroscopy in order to obtain information on reaction intermediates. Adsorbed NNx species are discussed as important intermediates in the N-2 and N2O formation. The absence of Pt results in a delay in HNCO ignition and only a small N2O formation is observed.