This work studied the process of electrochemical formation of polypyrrole, Ppy, over a graphite-epoxy resin composite electrode in the presence of different anions: DS-, NO3- and Cl-. It was shown by means of AFM that the morphological characteristics and the formation kinetics of the Ppy deposit, from analysis of experimental current density transients, are strongly dependent on the nature of the anion present. It was found that for all cases, the formation mechanism involves the simultaneous presence of adsorption and 3D nucleation, limited by diffusion of the different pyrrole oligomer species, processes. (c) 2005 Elsevier B.V. All rights reserved.