The new technique of time and angle resolved ultraviolet photoemission spectroscopy (UPS) is used to study electron dynamics at single crystal surfaces and interfaces in the picosecond time domain. A single laser source is used to photoexcite electrons into normally unoccupied states at a surface or interface and provides the UV radiation for photoemission studies of the excited system. In this paper we briefly review studies of the unoccupied surface state on the clean InP(ll0) surface and present new results for three related interfaces. We have studied the transiently excited Al/InP, O/GaAs, and Au/GaAs interfaces, and have for the first time directly observed with photoemission normally unoccupied interface states above the Fermi level in these systems. © 1986, American Vacuum Society. All rights reserved.