The electrocatalytic activity and stability of alkaline air electrodes have been studied. The results show that the stability of the electrodes is determined by a large number of factors. To obtain high reaction rates electrocatalyst with high exchange currents and high surface area is critical. However, it is of equal importance that the pore structure is correct. This determines the transport properties of oxygen, water and electrons to the reaction sites. In the choice of materials care has to be taken also regarding stability to obtain long lifetime at high activity. (C) 2004 Elsevier B.V. All rights reserved.