Abstract: The kinetics of O₂ anodic evolution was studied in alk.solution. The results show that the values of əψ/əlgi egual 39 mV and 120 mV at low and high currents, respectively, and that of əψ/əlga_OH-egual-2?39 mV at low currents and-120 mV at high currents. The kinetic data obtained show that the rate determining step of the anodic evolution of oxygen on Pt and mild steel electrode is MOH_ad+OH^-→MO_ad+H₂O+e The influences of Li⁺, Na⁺, K⁺, CNS^- and Cl^- ions on the reaction rate were discussed as well.