The electronic conductivity of polymers such as polyaniline exhibits a strong dependence on the redox and protonation state of the polymer. This property has been utilised to develop a generic biosensor concept. The concept involves immobilization of the appropriate enzyme in the conducting polymer matrix. The enzyme catalyzed reaction of the biomolecule results in a change in redox potential and/or pH of the micro environment in the polymer matrix. This change in the micro environment triggers a change in the electronic conductivity which is monitored. Results shall be presented which provide proof of the above concept. The systems chosen for investigation are glucose/glucose oxidase, urea/urease, neutral lipid/lipase and hemoglobin/pepsin.