The effect of the platinum particle size was investigated for the catalytic oxidative dehydrogenation of aqueous ethanol to ethanal at a temperature of 303 K, an ethanol concentration of 260 mol m(-3), a partial oxygen pressure 60 kPa, a pH of 9, and an ethanal and ethanoate concentration of 20 mol m(-3). A particle size effect on the turnover frequency was observed but only for particle sizes smaller than 2 nn. Hence, the reaction shows a limited structure sensitivity.