The initial stages of Hg0.8Cd0.2Te anodization have been studied by electrochemistry and x-ray photoelectron spectroscopy (XPS). Comparison of the polarization curves of HgCdTe, HgTe, and CdTe with XPS measurements of HgCdTe surfaces anodized to various potentials allows us to propose a possible model for the anodization. First the Hg-rich surface layer formed by the bromine–methanol etch is removed at a potential of ∠−0.1 V vs SCE (standard calomel electrode). Upon oxidation of the Te2− at ∠+0.35 V vs SCE in an aqueous solution (at ∠+0.6 V vs SCE in an ethylene glycol solution) the Cd2+ and Hg2+ ions are released, with the Cd2+ reacting with the Te4+ and O2− to form CdTeO3 and CdTe2O5. Some of the Hg2+ is incorporated into the oxide in analogous compounds, but most is driven into solution. The dissolution of Hg proceeds in advance of the Te4+/Te2− interface, resulting in a depletion of Hg from the interfacial region of the semiconductor.