The suitability of metallic aluminum as an electrode material for the preparation of a chemically modified electrode by the simple electroless procedure is described. As a typical example of modification, metallic nickel and nickel-hexacyanoferrate (NiHCF)-coated aluminum electrodes were prepared and their electrochemical characteristics were studied. Voltammetric investigations showed that the Ni and NiHCF-modified Al electrodes were electrochemically stable over the desired potential range 0-1.2 V in 0.25 M phosphate buffer solution of pH 4-10. The cyclic voltammograms of the NiHCF films, indicate the presence of a surface redox couple at 0.44 V, which corresponds to the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) system. The oxidation of ascorbic acid as a typical organic compound was examined on the modified electrodes. A well defined and reproducible anodic peak was observed. The NiHCF films, formed on the Al electrode show an excellent electrocatalytic activity towards the oxidation of ascorbic acid in phosphate buffer solution of pH 7.2. The kinetics of the catalytic reaction were investigated using a rotating disk electrode voltammetry. The results obtained for various thicknesses of the film and ascorbic acid concentrations are explained using the theory of electrocatalytic reactions at chemically modified electrodes. The rate constant for the catalytic oxidation of ascorbic acid and the diffusion coefficient of electrons in the film were calculated. Further examination of the modified electrodes shows that the modifying layers (Ni and NiHCF) on the aluminum substrate have reproducible behaviour and a high level of stability.