The reversible change in photoluminescence intensity with change in gaseous ambients (N2, Ar, H2, O2, H2O, and vacuum) from a InP cleaved (110) surface and the irreversible change in photoluminescence from a GaAs cleaved (110) surface when exposed to oxygen were observed at room temperature. These phenomena imply that adsorbed N2, H2, Ar, H2O, and O2gases can be exchanged reversibly on the InP surface, and the surface recombination velocity changes reversibly with the adsorbed gas species. On the other hand, oxidation proceeds rapidly and irreversibly on GaAs cleaved surfaces.