AbstractThe technique of attenuated total reflection spectroscopy has been introduced into the study of photooxidation of organic dyestuffs adsorbed at semiconductor electrodes. Using a ZnO electrode itself as the internal reflection element, an internally reflected laser beam served simultaneously as the actinic radiation and as a measuring beam to monitor the absorption of the adsorbed dye layer. Correlation of these data with the photocurrent produced by oxidation of the dye yielded a measure of the quantum efficiency, Φ, for photooxidation of the adsorbed dye. The dye‐semiconductor system rose bengal‐ZnO was studied to demonstrate the capabilities of this technique.