The electrochemical behavior and stability of Pt, Ti, TiN, and nano-porous carbon for implantable cardioverter-defibrillator (ICD) electrode application were investigated in a phosphate buffered saline solution. The electrochemical interfacial proper-ties were examined by electrochemical impedance spectroscopy, and the potential and current response during ICD shock pulses were recorded by a digital oscilloscope. Changes in surface composition and structure were investigated using X-ray photoelectron spectroscopy and environmental scanning electron microscopy. When exposed to anodic 700 V shock pulses with duration of 10 ms, only Pt was stable, nano-porous carbon electrode was slightly attacked, whereas Ti and TiN electrodes suffered severe degradation. Upon cathodic shock pulsing, all the materials were stable, but Ti and TiN electrodes with a smooth surface showed evidence of hydrogen adsorption. Porous and rough electrodes produced less gas evolution compared to a smooth surfaces, due to a higher amount of charge transferred through non-Faradaic processes. The reason for this could be higher interfacial capacity due to the large surface area. (C) 2004 Elsevier Ltd. All rights reserved.