We report the results of quantum-chemical and ab initio molecular dynamics studies within the framework of density functional theory for the oxidation of methanol on the (1 1 1) face of a platinum single crystal. In aqueous solution the oxidation of methanol starts by the formation of a hydrogen bond from the OH group of the methanol to a solvent molecule. The initial step of the reaction is the cleavage of a CH bond which points towards the platinum surface; this is followed by rapid dissociation of the methanol OH bond, which leads to formaldehyde as a stable intermediate on the time scale of the simulation. Charge delocalization is achieved by the formation of a Zundel ion View the MathML source in the aqueous phase. The further evolution provides hints for the following steps of methanol oxidation and proton conduction in the environment of a liquid-fed direct methanol fuel cell.