Abstract: An electrode for use in electrochemical ion exchange comprises an electrically conducting element covered by at least two layers of ion exchange material. The material in one layer differs in its electrical, chemical, or ion exchange properties from that in an adjacent layer. For example a thin layer of cation exchange material underneath a thicker layer of anion exchange material may be used to inhibit the oxidation of chloride ions; a thin layer of cation exchange material covering a thicker layer of anion exchange material provides an anion-responsive electrode with enhanced selectivity for particular ions. An ion-selective anion-responsive electrode can also comprise a thin outer layer of a very weak base anion-responsive material, covering a thicker layer of a strong base material of lower electrical resistivity.