A clean rhodium filament at room temperature is highly reactive towards nitrous oxide. The oxygen atom of the N 2O molecule is adsorbed with a sticking probability of 0.45 whilst the nitrogen atoms appear in the gas phase as molecular nitrogen. The room temperature uptake of oxygen is about 5 × 10 14 atom cm -2 and is independent of nitrous oxide pressure in the range 3.5 × 10 -8 to 1.1 × 10 -6 torr. The adsorption curve is of typical form with an initial region of essentially constant sticking probability. For the first 80% of adsorption at room temperature the shape is satisfactorily accounted for if molecules are able to visit 4-5 adsorption sites whilst held in a weakly-bonded precursor state.