The influence of the mass transfer on the electrochemical oxidation of methanol was investigated at a rotating disk electrode with smooth polycrystalline Pt and high area carbon supported Pt (Pt/C) as the electrocatalysts. It was found that the reaction rate at the smooth Pt is suppressed significantly by the convection of the electrolyte. The Tafel slope and the reaction order with respect to methanol were also influenced by the convection of the electrolyte. On the contrary, mass transfer influenced neither the reaction rate nor the kinetic parameters of methanol oxidation at the Pt/C electrocatalyst. It was proposed that a reaction path via formaldehyde as a soluble intermediate is operative at both electrocatalysts, but with hindered diffusion of formaldehyde from the corrugated surface of the Pt/C. (C) 2004 Elsevier B.V. All rights reserved.