The electrochemistry of conducting and non-conducting electropolymerised films have been evaluated for the construction of enzyme electrodes. Poly(phenol red) and poly(pyrrole) films were studied using a.c. impedance, spectralreflectance, and linear and cyclic voltammetry. The reflectance properties of poly(phenol red) films were shown to be influenced by solution pH. The application of an oxidising polarising potential caused the reflectance pH profile to be displaced to more basic regions which is thought to be due to minimised proton partioning into the poly(phenol red) film. Voltammetry studies of poly(phenol red) in monomer free solution revealed a quasi-reversible pH dependent 2e-/2H + reaction within the film. A possible structure of poly(phenol red) is proposed here based on a phenol linkage mechanism. A.C. impedance spectroscopy was used to study glucose oxidase containing poly(pyrrole) films. Addition of glucose substrate caused an increase in film resistance, an effect reproduced by using one of the products of the glucose oxidase reaction, H202. Similar resistance changes were observed when ferricyanide was substituted for O 2 as the electron acceptor. Changes in poly(pyrrole)/glucose oxidase film resistance could be correlated to glucose concentration by either co-immobilising catalase with glucose oxidase, or by providing excess ferricyanide in the electrolyte solutioin. For both thin film types used poss~le mechanisms for pH and product dependent changes have been elucidated.