Adsorption and decomposition of NO on Pt (1 1 2) have been studied by temperature programmed desorption (TPD), ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). NO adsorbs molecularly on Pt (1 1 2) at 95 K. About half amount of NO molecules adsorbs at the terrace sites and remaining half amount adsorbs at the step sites at a full monolayer coverage. Then about half of:NO molecules adsorbed at step sites decomposes at around 483 K desorbing N-2, promptly