We report studies of the stability of single crystal surfaces of Hg1-xCdxTe with respect to loss of Hg. Ultraviolet photoemission spectroscopy (UPS) and X-ray-induced photoemission (XPS) were used to monitor the electronic structure and atomic composition of a cleaved surface under ultrahigh vacuum (UHV) (p ≅ 5 x 10-10 Torr) and under oxygen exposures. These experiments showed the surface to be remarkably stable in UHV for extended periods of time at room temperature. However, changes in the surface concentrations can be induced during exposure to excited oxygen or during ion bombardment. The importance and relevance of these findings to the question of the stability of the material are discussed.