In the majority of impedance spectroscopy experiments performed for characterization of the semiconductor vertical bar electrolyte interface, mass transport effects produce a diffusional element in the impedance spectrum. We report here, results obtained in the heart that has been perfused for cardioplegia with Tyrode's buffer. Electrodes employed include polypyrrole, polyaniline, poly(3-methylthiophene), and poly(3,4-ethylenedioxythiophene). With the exception of a small, approximately constant-Im{Z} element (possibly related to the back junction), metallurgically perfect poly(3,4-ethylenedioxythiophene) electrodes exhibited Ohmic behavior. Such an electrode is important for sensing of biological signals since it does not suffer from the high-pass filtering traceable to charge accumulation at conductor surfaces, thus implying removal of Gouy-Chapman-Stern reactances. (c) 2005 Elsevier B.V. All rights reserved.