The electropolymerization of neutral red on glassy carbon (GC) electrode has been studied by means of in situ UV-Vis spectroscopy and cyclic voltammetric measurements to understand the role of electro-initiation process during the electropolyrnerization. The experimental results show that a radical-cation was produced during the electro-initiation at a higher potential. And the radical-cation can lose a hydrogen ion to generate a radical, the latter can react with another monomer to the other radical or react each other to form a dimer or an oligomer, which can be more easily oxidized at a lower potential. Consequently after the electro-initiation the electropolymerization of neutral red can well be accomplished in a relatively narrow potential range and the good poly(neutral red) films can be obtained. ESR spectra also demonstrate the formation of radical in the poly(neutral red). Furthermore FT-IR spectra show that main characteristic absorption peaks of neutral red change accordingly after the electropolymerization. (c) 2006 Elsevier B.V. All rights reserved.