Using argon and krypton lasers the photon assisted tunneling of electrons from aluminum into the SiO2 conduction band was observed for the first time. The data are found to be in excellent agreement with a simple model assuming an AlSiO2 barrier height of 3.15 eV and an electron effective mass in the SiO2 band-gap of 0.5m. The results are consistent with the conclusion that the classical image force barrier lowering does not contribute to tunneling. The technique is promising for the study of interface phenomena. © 1976.