The electro-polymerization of 3,4-ethylenedioxythiophene (EDOT) on highly oriented pyrolytic graphite (HOPG) in aqueous media has been investigated by current-time transient measurements and atomic force microscopy. Deposition involved an initial step, in which the whole electrode was essentially covered with an increasing number of nuclei. This first step occurred at very short times (less than 3 ms at high driving force) and was followed by further growth, the nature of which depended on the magnitude of the applied potential. At high driving force, a progressive 3D mechanism took place, while a 2D layer-by-layer process was observed at low driving force. These observations provide a simple means of controlling the morphology of electrodeposited poly(3,4-ethylenedioxythiophene). (C) 2008 Elsevier B.V. All rights reserved.