A detailed study of the mechanism of the electroreduction of O-2 in alkaline solutions on a stable reconstructed surface of polycrystalline gold is presented. The observed polarization curves are (100)-like. A current maximum corresponding to four electrons per molecule of O-2 reacted is observed in the low-overpotential region; evidence is given that a regenerative mechanism is then operative. At potential values below the potential of the maximum, the number of electrons per O-2 molecule reacted decreases and becomes smaller than the number observed for the original Au surface. The links between the electrochemistry of the original and reconstructed Au surfaces in the so-called double layer region and the details of O-2 reduction on those surfaces are discussed.