Copolymers prepared from 3,4-ethylenedioxythiophene (EDOT) and Diclofenac (DCF) through cyclic voltammetric method exhibited electroactive and electrochromic behaviours. Addition of DCF produced bathochromic shift of the MOT main absorption band from 253.4 to 269.7 nm in the UV-vis spectra. The cyclic voltammetric studies were carried out with different feed concentration of DCF and in the presence of two different surfactants, SIDS and CTAB on glassy carbon electrode surface. Effect of scan rate on the three types of electroactive copolymer films was studied. The three different copolymers showed good adherence on the glassy carbon electrode surface in aqueous 0.1 M KCl medium. Spectroelectrochemical analysis of copolymer film was carried out on Indium-Tin-Oxide (ITO) plate and it showed multicolor electrochromic behaviour when the applied potential was changed. The color of the copolymer was changed from neutral yellow to brown and to violet in 0.1 M KCl medium. Among the three different copolymers, the copolymer prepared in presence of CTAB resulted in high contrast colors. The electrochromic parameters such as coloration efficiency, optical contrast, response time and stability were also evaluated. The surface morphology of the copolymer films was characterized by SEM analysis. (c) 2005 Elsevier Ltd. All rights reserved.