The luminescent electrooxidation of methanol in aqueous sodium hydroxide on a glassy carbon electrode has been characterized. Two different mechanisms appear to exist, depending on both the CH3OH concentration and the potential. A major mechanism may be associated with the electrooxidation of the methoxide ion (CH3O-) to formaldehyde (HCHO) via disproportionation of anodically generated methoxyl radicals (CH3O .). This mechanism is predominant when the CH3OH concentration is less than or equal to 0.1 M, and results in luminescence with a broad spectral distribution (peak around 550 nm). Another major mechanism may involve the production of excited singlet oxygen (O-1(2)) via a tetraoxide. Either with higher CH3OH concentrations or at more positive potentials, the latter pathway predominates, producing red luminescence with a peak at around 640 nm.