The selective oxidation of aqueous ethanol by dioxygen over a platinum on carbon catalyst was investigated in a three-phase continuously stirred tank reactor at a total pressure of 600 kPa, a temperature of 323 K, a pH of 8.4, and a catalyst concentration of 2.3 kg m(-3). Multiple steady-states were obtained by systematic changes in the start-up procedure and variation of the feed concentration of ethanol and partial oxygen pressure in the reactor. The ethanol feed concentration was varied from 100 to 2500 mol m(-3) and the partial oxygen pressure from 8 to 120 kPa. On the time scale of the experiments, i.e. 21 ks, two steady-states of the net disappearance rate of ethanol are observed in the ethanol feed concentration range from 500 to 2500 mol m(-3) at a partial oxygen pressure of 58 kPa and in the range of partial pressure of oxygen from 8 to 120 kPa at an ethanol feed concentration of 500 mol m(-3). Three steady-states are observed in the feed ethanol concentration range from 200 to 400 mol m(-3) and a partial oxygen pressure of 58 kPa.