In this paper, oscillatory electrodissolution of Al in perchloric acid solutions has been investigated. The Al/HClO4 system is a new electrochemical oscillator and particularly, current oscillations occur over a large range of HClO4 concentration and over a wide scale of applied potential. The effects of the applied potential and the HClO4 concentration on the current oscillations have been studied. The results are discussed in terms of the formation and dissolution of the surface oxide film. During the anodic dissolution of the Al electrode in HClO4 solutions, perchlorate ions are reduced to chloride ions, by which, pitting corrosion is induced. The surface morphologies of Al electrodes observed using an environmental scanning electron micrograph show that it is pitting corrosion that induces the current oscillations. (C) 2004 Published by Elsevier B.V.