Bilayer lipid membranes (BLMs) after suitable modofications have been reported as sensitive and selective electrochemical probes for inorganic ions. They are prepared as follows: when a metalic wire covered with a Teflon tubing has been cut in the organic phase and put into an aqueous solution, the amphiphilic lipid molecules in the solution have aligned at the interfaces of a metal/organic and organic/aqueous phases which resulted in the formation of the self-assembled solid supported bilayer lipid membranes (s-BLMs). With the modification of crown ether molecules in the s-BLMs, the membrane potentials were observed to show Nernst response to the concentration of metal cations in the range of 10−4– 10−1mol.dm−3.