The electrooxidation of 2-chlorophenol (2-CP) on poly-nickel tetrasulfophthalocyanine (polyNiTSPc) modified glassy carbon (GC) and indium tin oxide (ITO) electrodes was studied by cyclic voltammetry and in situ UV-Vis transmission spectroscopy. The polyNiTSPc films were characterized by XPS and AFM, both before and after reaction with 2-CP. The results indicate that NiTSPc polymerizes at both GC and ITO electrodes, apparently retaining its phthalocyanine structure in which the Ni atoms play a role similar to that in Ni(OH)(2) films. In the oxidation of 2-CP at polyNiTSPc-modified electrodes the electrode fouling by a layer of polymerized 2-CP oxidation products (polyCP) is weaker than on the bare GC electrode, probably because the polyCP layer formed on polyNiTSPc-ITO is very rough, as indicated by AFM, thus allowing the passage of CP molecules to the polyNiTSPc film. (C) 2003 Elsevier Science B.V. All rights reserved.