It was demonstrated that, in contrast to previous results, an NCO surface complex does form on Au/TiO2 catalysts in the high-temperature reaction of NO+CO. By means of Fourier transform infrared spectroscopy two new absorption bands at 2180 - 2190 and 2205-2210 cm(-1), not observed in separate adsorption of reacting gases, were detected during the catalytic reaction. The former is attributed to Au - NCO and the latter to Ti - NCO species. It was assumed that, similar to the case of supported Pt metals, NCO is primarily formed on Au crystallites and then spills over onto titania. This idea was strengthened by the results obtained following the adsorption of HNCO on the catalyst and on the support.