Voltammetric and UV-Vis spectroelectrochemical studies on 4-aminophenol (4-AP) at gold electrodes have been carried out in conventional electrochemical and in novel spectroelectrochemical cells. As base electrolytes acetonitrile with 10(-2) M tetrabutylammonium hexafluorophosphate as supporting electrolyte and acetate buffer (pH 4.6) solutions have been used. 4-AP was electrochemically oxidized at gold electrodes at potentials > +0.1 V in aqueous solutions and at potentials > +0.5 V in acetonitrile solutions. The formation of an oxidation product has been characterized in situ by UV-Vis spectroscopy in a novel optical thin-layer spectroelectrochemical cell. (C) 2003 Elsevier Science Ltd. All rights reserved.