Nitrous oxide(N2O) interacts at room temperature and low pressure (> 10(-5) mbar) with Fe(II) species in both Fe-MCM-41 and Fe-ZSM-5, to form adsorbed nitric oxide. The adsorbed product is identified by its characteristic but different N=O stretching frequencies on these two materials, and also by chemiluminescent analysis after desorption at T>420 K. It is proposed that the other product of N2O decomposition is nitrogen. This decomposition is thermodynamically favourable, due not least to the heat of adsorption of the adsorbed NO formed. Catalytic N2O decomposition, forming nitrogen and oxygen, does not occur until T>770 K, probably by a different mechanism.