Electrochemical impedance spectros- copy was used to study the impedance of an electrode-electrolyte system. For the stimulation and recording of natural neural networks a low impedance is required; hence the need for a full impedance characterization. The electrode materials investigated were bright Pt, Pt-black and TiN; the electrolyte was 0.9% aqueous NaCl. An equivalent circuit model has been established. The effect of surface roughening has been investigated. Cyclic voltammetry was used to obtain the exchange current density of bright Pt. MEASUREMENTS & RESULTS: The measure- ments were performed using a three electrode apparatus: calomel reference electrode and Pt counter electrode with a commercially available potentiostat (Autolab PGSTAT 30) and frequency response analyzer (ECO Chemie B.V., NL). Both Pt- black and TiN have dendritic surface structures, and are used here to explore the effect of surface roughness.