A highly porous carbonized polyacrylonitrile microcellular foam with very low platinum loading (approximately 13 to 23 mu g cm(-2)) was prepared for use as a possible electrode material in a fuel cell system, The effective surface area of platinum at the PAN/Pt electrode is estimated to be about 1.4 times the geometric area of the substrate electrode. The average particle size deduced from the electrochemical measurements is 44.9 nm. The electrochemical reduction of oxygen was studied at this material by using the rotating disk electrode method, Scanning electron microscopic images of this material clearly show the existence of nanometer sized platinum particles that are homogeneously distributed. These platinum particles are somewhat "isolated" from each other, within the carbonized PAN matrix that is highly porous with a pore size ranging from ca. 1 to 10 mu m. The reaction order for the oxygen reduction on this material is unity. The results show that the O-2 reduction at the PAN/Pt electrode involves an overall transfer of four electrons per O-2 molecule consumed.