The present work is motivated by attempts in our laboratory to develop the physical basis for the design of biosensors (suited for aqueous medium) based on biofunctional supported membranes as receptor surfaces. We study the electric properties of supported lipid membrane on modified silicon electrode with impedance spectroscopy. To functionalize the silicon wafers. a thin layer of silicon dioxide (SiO2) was grown by wet oxidation. The thin layer has been characterized by X-ray photoelectron spectroscopy (XPS), electrical impedance spectroscopy and cyclic volatammetry. We prepared electrolyte-membrane-electrolyte-semicon (EMES) interface by fusion of positively charged lipid vesicles (containing 50 mol% DOTAP and 50 mol% cholesterol) on Si/SiO2 electrodes. Membrane resistances up 30 k Omega cm(2) were reached. By impedance spectroscopy it is possible to discriminate between changes of the capacitance of the silicon electrode and the membrane capacitance.