Electrochemical communication between the redox active centre of the enzyme horseradish peroxidase (E.C.1.11.1.7), HRP, and the conducting polymer, poly(aniline), is shown to be possible and efficient at pH 5. The interaction between HRP and the poly(aniline) film was studied employing flow injection analysis. The modified electrodes employed consisted of two carbon band electrodes (ca. 10 µm wide, 4.5 mm long separated by a 20 µm gap) coated with an anodically grown film of poly(aniline). HRP was deposited on top of the poly(aniline) film in one of two ways. In the first HRP was immobilised onto the poly(aniline) film in an insulating poly(1,2-diaminobenzene) polymer grown electrochemically on top of the poly(aniline) film. In the second, HRP was absorbed on to the surface of a poly(aniline) modified electrode. The effect of the potential of the poly(aniline) film and ‘phenazine’ concentration within the film on the efficiency of interaction between the redox centre of HRP and the conducting polymer film are reported.