The simultaneous adsorption of pure hydrogen and nitrogen on polycrystalline tungsten, at. 300 °K, has been compared with the adsorption of the pure gases on the same surface. The results are consistent with a model which assumes a single set of adsorption sites, equally accessible to either gas, with only weak interaction between the two adsorbed species. The sticking probability and rate of adsorption of each gas is primarily determined by the fraction of the adsorption rates covered and is relatively independent of the particular species in the adsorption sites. There was no evidence of the replacement of one gas by the other at 300 °K.