The adsorption and desorption of nitrogen on a platinum filament have been studied by thermal desorption techniques. Nitrogen adsorption becomes significant only after any carbon contamination is removed from the surface by heating the platinum filament in oxygen, and after the CO content in the background gas is reduced substantially. At room temperature nitrogen populates an atomic tightly bound β-state, E≠ = 19 kcal mole−1. The saturation coverage of the (3-state is 4.5 × 1014 atoms cm−2. Formation of the (β-state is a zero order process in the pressure range studied. At 90 K two additional α1- and α2-desorption peaks are observed. The activation energy for desorption for the α2-state is 7.4 kcal mole−1 at low coverage decreasing to 3 kcal mole−1 at saturation of this state, 6 × 10 molecules cm−2. The maximum total coverage in the α-states was 1.2 × 1015 molecules cm−2. A replacement process between the β- and α-states has been observed where each atom in the (β-state excludes two molecules from the α-state.