A highly dispersed platinum catalyst (platinum crystallite size less than 15Aå) on a conductive carbon support was prepared. These doped carbons were made into Teflon‐bonded fuel cell electrodes and the platinum surface area and the dispersed platinum specific activity (i.e., the activity per unit area of platinum) for oxygen electroreduction in acid electrolyte was determined. The specific activity of the dispersed platinum was found to be approximately twenty times less than that of crystalline platinum black. The lower activity of this catalyst compared with that of platinum black may be due either to the difference in the platinum crystallite sizes, or to the influence of the support on the platinum activity, or to a combination of both these factors.