The first part of a study of the electroreduction of dioxygen on different polycrystalline platinum surfaces in 1 M NaOH is reported. The results presented refer to a platinum surface that was pretreated by cycling the applied potential between 40 and 1450 mV. The rotating ring-disk electrode polarization curves for the reduction of O-2 show hysteresis, which is observed within the entire potential range explored (40 to 1450 mV), increases as the rotation rate increases, is specially large above 300 mV and significantly decreases when the disk is coated with a Nafion film, mainly as a result of the increase of the current intensity in the anodic scan (which is especially observed within the 300-700 mV potential range and indicates significant HO2- disproportionation in this range). These polarization curves entirely follow those recorded for the reduction of HO2- both in the cathodic and in the anodic scan, clearly showing that the reduction of O-2 on this platinum surface is completely dependent on how the surface deals with the HO2- formed during the O-2 reduction process. The details of the polarization curves are discussed in relation to the details of the surface electrochemistry revealed by the correspondent cyclic voltammogram.