Electrochemical oxidation of phenolic compounds leads to a deposition of polymeric films on the surfaces of Pt, glassy carbon, pyrolytic graphite and carbon fiber electrodes, decreasing the electrode activity (passivation). Addition of EDTA to the medium produces a significant enhancement in the electrochemical behavior of phenolic compounds, avoiding electrode passivation. An improvement in the selectivity and sensitivity for the quantitative voltammetric determination of dopamine, catechol and 4-aminophenol was also verified. The electroactivity of the electrode was maintained even after long periods of use in the presence of EDTA. The effect of the EDTA concentration on the electrochemical behavior of some phenolic compounds is reported. (C) 2003 Elsevier Science B.V. All rights reserved.