The results of experiments and calculations on the oxidation of methanol are presented in this paper. The oxidation process was considered under conditions of constant current. Experimental measurements reveal that the oxidation of methanol exhibits a response in which three different branches of steady-state potentials exist under the same conditions. Characteristics of the measurements and the present understanding of the electrochemical mechanism are consistent with the hypothesis that the two lower branches coexist because an intermediate, surface bonded CO, can react with both surface water molecules and surface bonded hydroxyl radicals. Calculations show that the coexistence of the two lower branches of states can exist because of the two reactions. Calculations reveal also a feedback mechanism that causes the system to make a transition between the two branches. The latter instability has practical importance, as it can cause a methanol-air fuel cell potential to drop suddenly.