We present a combined cyclic voltammetry and electrochemical quartz-crystal micro-balance study of a thin-layer germanium electrode in 1 M HClO4 electrolyte. When the potential is more positive than -0.2 V versus SCE, significant mass loss occurs due to anodic dissolution. However, when the potential is cycled in a range below -0.2 V versus SCE, only periodic variations of mass are observed, corresponding to the quasi-reversible change of the surface between a hydrogenated state and a hydroxylated state. These data provide the as yet missing clearcut proof that this change of state takes place without any dissolution of the electrode. (C) 2003 Elsevier Science B.V. All rights reserved.