Stable and reversible electrochemical responses of cytochrome c can be measured on bare unmodified gold and glassy carbon electrodes. It has been found that in phosphate buffers the electrochemical behaviour varies from completely irreversible to reversible on both electrodes depending on the concentration of the supporting electrolyte. The optimum phosphate concentration was found to be between 20 and 30 mM. It was also observed that the electrochemical response improved with the lifetime of the protein samples and could be destroyed by mechanical aggregation of cytochrome c molecules. The importance of oligomeric forms of cytochrome c on the electrode surfaces was emphasized; they determine the overall electrochemical behaviour.