The impedance characteristics of parchment-supported inorganic precipitate model membranes have been analyzed in order to understand the mechanism of ionic diffusion through biomembranes. The observed values of membrane capacitance and resistance were found to be dependent on the concentration of bathing electrolyte and applied oscillator frequency. The change in membrane capacitance and resistance values with the change in electrolyte concentration and oscillator frequency has been interpreted in terms of changes produced in the electrical double layer at the membrane–solution interface. The values of interfacial double layer capacitance derived by the equations of Armstrong and Longer were found to be different due to the presence of polarising charge and other structural details of membrane matrix. Different model-equivalent electrical circuits have been analyzed using the experimental data. The complex impedance spectra have been found to deviate from the theoretical predictions at low frequencies due to nonhomogenous and rough surface of the membrane.