Electrochemical impedance measurements were performed on two different molecular assemblies that were created in order to mimic living cell membranes. In the first, a bare gold electrode surface was used as a support for Langmuir-Blodgett transfers of mono-, bi-, and multilayers of dipalmitoylphosphatidic acid. In the second, a thin polyelectrolyte film was self-assembled on the gold surface prior to the Langmuir-Blodgett transfer. A small membrane resistivity, i.e. 100-300 Omega cm(2), was observed across the phospholipid bilayer when deposited on the polyelectrolyte surface provided the outermost layer was polyanionic. The contribution to the total membrane capacitance from one monolayer in these assemblies was 1.16 mu F cm(-2). Similar results for the membrane capacitance were obtained in multilayer assemblies of more than five monolayers when the support was a bare gold electrode surface, whereas thinner multilayer assemblies displayed significantly higher capacitances. Furthermore, the main contribution to the membrane resistance in the latter case was shown to originate from resistances in defect pores, through which the double-layer capacitances at the ends and inside these defects were charged.