The adsorption of nitric oxide (NO) on a Cu(100) surface at 25 K has been studied using infrared reflection absorption spectroscopy (IRAS). Initially, NO adsorbs at the bridge site; however, with an increase in coverage, dimerization of NO occurs. Further dosing of NO at 25 K produces a multilayer of the NO dimer. Annealing this dimer multilayer to 40 K causes a change in the alignment of the dimers in the multilayer with respect to the Cu(100) surface. Heating to 55 K leads to reorientation of the dimer molecules in the multilayer such that the N-N axis becomes perpendicular to the surface; at 60 K the multilayer NO dimers desorb. Formation of N2O was observed upon heating the surface above 60 K.