The NOx desorption profiles obtained in O2-He and n-C10-O2-He were compared on γ-Al2O3 and Ag/γ-Al2O3. On Ag/γ-Al2O3, the low-temperature NOx desorption profiles obtained in n-C10-O2-He were significantly different from those obtained in O2-He. In particular, at 190-220 °C excess release of NO, instead of NO2, was observed concomitantly with n-C10 consumption. This is interpreted as the result of the formation-decomposition of organo-NOx species issued from the interaction of NO2 and hydrocarbons initially chemisorbed on Al2O3 and activated on Ag species, respectively. The occurrence of such a phenomenon at temperatures close to those at which the n-C10-SCR reaction starts provides support for the involvement of the organo-NOx species as intermediates.