The adsorption of nonexcited molecular oxygen on ordered and disordered(110) surfaces of GaAs was studied using photoemission techniques. On the ordered surface, only one chemically shifted level was observed for the As3dcore level up to 1013exposure. The Ga3dcore level exhibits an asymmetrical broadening towards higher binding energy for the same exposure, indicating the presence of a shifted component. The percentages of shifted Ga and shifted As appear to be about equal. However, when a sputtered (disordered) surface was exposed to oxygen, there was preferential adsorption on the Ga. Implications of these data are discussed.