Over the last decade, there has been considerable interest in the development of immunoelectrochemical assays, mainly due to the advantages offered by the combination of the selectivity of immunoassays with the great sensitivity and simplicity of modern electroanalytical techniques. However, immunoelectrochemical assays have not yet been exploited commercially, as transitions from the laboratory bench to large-scale manufacturing has proved difficult. The system described is an amperometric peroxide biosensor prepared by electrochemical deposition of horseradish peroxidase on an electroactive polymer, polyaniline. Polyaniline brings about mediatorless redox coupling between the electrode and biomolecular components attached to the surface. This assay will be the stepping-stone to developing an immunoelectrochemical method for the analysis of human chorionic gonadotropin (hCG), and other female hormones. The assay initially utilises glassy carbon electrodes for preliminary data, before being replaced with a commercially available electrode Euroflash TM, produced by Inverness Medical Limited TM. This electrode was utilised with a view to producing an electrochemical assay that complies with manufacturing requirements.