The influence of ethanol on the passivating films on Ni and Fe electrodes in 1 M NaOH was studied by cyclic voltammetry and potential-modulated reflectance (PMR) spectroscopy over a wide potential range. The decrease in the PMR maximum attributed to NiOOH which occurs when ethanol is added clearly shows that ethanol produces a decrease in the thickness of the NiOOH layer on the Ni electrode; this effect increases in a nearly exponential way with the potential, reaching near saturation at an ethanol concentration of 1 M. A similar, but much smaller, decrease in the FeOOH layer on iron is also produced by ethanol. In contrast, neither the passivating NiO on Ni nor the passivating Fe(III) oxides on Fe are attacked by ethanol. Since only the Fe and Ni oxyhydroxides are attacked by ethanol, while the passivating oxides are not, it is concluded that in order to react with ethanol the anodic oxides of Fe and Ni must have hydroxyl groups.