Polypyrrole, poly( 3,4- ethylenedioxythiophene) and the copolymer of pyrrole and 3,4- ethylenedioxythiophene films were synthesized electrochemically on carbon. fibre microelectrodes ( CFME). Deposition conditions on the carbon. fibre and the influence of monomer concentrations on the copolymerization, as well as the electrochemistry of the resulting polymers and copolymers, were studied. Structural studies of the polymers were conducted using different techniques such as cyclic voltammetry, in situ spectroelectrochemistry, FTIR and scanning electron microscopy. The effect of the monomer ratio on the formation of copolymer is reported. A high level of stability to overoxidation was also observed for poly( 3,4- ethylenedioxythiophene) as the polymer on this CFME substrate shows limited degradation of its electroactivity at potentials 1.2 V above its half- wave potential.