Cobalt-carbonized aerogel nanocomposite was prepared from highly porous polyacrylonitrile microcellular foams containing a salt of cobalt, followed by carbonization. The electrochemical reduction of oxygen was studied at this material by using the rotating disk electrode method. Good electrocatalytic activity for oxygen reduction at this material was demonstrated under experimental conditions close to those of a fuel cell cathode, that is, at the catalyst/Nafion((R)) interface in acidic solutions. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.