The effects of hydrogen on the electronic structure of the passive film on iron were investigated by photoelectrochemical methods. It was found that hydrogen increases the magnitude of the photocurrents from the passive films formed at all investigated potentials, and decreases the bandgap energies of the passive films formed at potentials lower than 0.6 V, implying that hydrogen can affect the bond strength of the oxides comprising the passive films. Increasing the film formation time increases the magnitude of the photocurrent from the passive film on the charged specimens more significantly than that on the uncharged specimens. In addition, chloride ion shows a different influence on the magnitudes of the photocurrents from the passive films on the uncharged and charged specimens. The magnitude of the photocurrent from the passive film on the uncharged specimen is hardly influenced by chloride ions, whereas the magnitude of the photocurrent from the passive film on the charged specimen is decreased due to the presence of chloride ions in the solution. Measurements of photocurrent transient behavior show that as a result of the presence of hydrogen in the passive film, the peak value of the photocurrent becomes smaller than that of the cathodic dark current, which is contrary to the photocurrent transient behavior of the uncharged passive film. The change in photocurrent transient behavior of the passive film caused by hydrogen also suggests that hydrogen can influence the electronic structure of the passive film. (C) 2003 The Electrochemical Society.