An approach to the microscale patterning of metal surfaces called "focused electric field-induced ion transport" (FEFIIT) is introduced. This process is a modification of the noncontact through-mask electrochemical etching method, in which an ion-selective membrane separates the anodic and cathodic electrolyte volumes. The membrane allows for a low metal ion concentration near the anode. The electric field near the workpiece can be modified by means of a perforated insulated mask parallel to the membrane surface. The performance of the FEFIIT process is studied both experimentally and computationally. Recommendations for process improvement are provided. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3496405] All rights reserved.