The electrochemical oxidation of H2O2 at a platinum rotating disk electrode was studied at pH 7.26 for the [H2O2] range 0-80 mM and for rotation rates 630-10,000 r.p.m. A mechanism is proposed to account for the steady-state current response as a function of both relation rate and [H2O2]. The mechanism incorporates reversible binding of hydrogen peroxide to electrochemically generated Pt(II) surface sites with inhibiting competitive adsorption of dioxygen at these sites. A further inhibiting side reaction is also identified involving protonation of the surface adsorbed H2O2 complex.