This article concerns the efficient dioxygen (O-2) reduction by a novel catalytic system that is comprised of two catalysts: one for the electroreduction of O-2 through the two-electron process and the other for the subsequent chemical decomposition of hydrogen peroxide generated. Here we represent the combined catalytic system of cobalt phthalocyanines and manganese oxide (MnOOH). Each catalyst performs well independently, leading to the totally four-electron reduction of O-2 in alkaline media. This was confirmed from almost twofold increases of the cathodic current in cyclic voltammograms and the steady-state current in rotating ring disk electrode voltammograms, the collection efficiency and the number of electrons calculated from the Koutecky-Levich plot. As a consequence, it is concluded that this combined catalytic system works efficiently for the O-2 reduction. (C) 2004 The Electrochemical Society.