A simple electrochemical method is presented to remove the bottom barrier layer of anodic aluminum oxide (AAO). In this method, an electrolysis process was performed in neutral KCl solution with AAO as the cathode. By applying a suitable cathodic potential, electrolyte temperature, and electrolysis time, the bottom barrier layer can be selectively dissolved by the etching of OH(-)ions without disrupting the porous alumina structure. The cathodic polarization behavior was studied to illustrate the electrochemical dissolution mechanism and its influence on the AAO/Al electrode. This study provides broader potential applications of AAO in the fields of electronics, magnetics, photocatalysis, microsensors, and so on. (c) 2007 The Electrochemical Society.