The research program Core Unit B.2, Electrode Fabrication, of the National Science Foundation/Engineering Research Center (NSF/ERC) is described. The program focuses on the development and fabrication of plunge, surface, and three-dimensional electrode arrays for measuring biopotentials. This unit is adapting existing semiconductor and microelectronics technology to produce the arrays needed for potential electrodes in basic arrhythmia studies and as mounting substrates for ion-selective and bioselective chemical sensors. The first two generations of Kapton-based microelectrode arrays were built on silicon and molybdenum substrates. Silicon integrated-circuit fabrication technology was used to demonstrate that surface electrode arrays can be formed. Two methods of interconnection for acute studies were developed.