Photon- or electron stimulated desorption (PSD or ESD) from solid surfaces results from the excitation of localized surface or adsorbate electronic states. The fundamental issues include the identification of electronic excitations with lead to desorption, the mechanisms for localization of the excitation, and the competition between nuclear motion and quenching of the excited states. We discuss these basic issues and their role in understanding stimulated desorption of molecular adsorbates from metal surfaces, and the desorption processes important in electron or photon bombardment of ionic solids. We focus on simple systems which serve as useful prototypes: CO chemisorbed on metals for adsorbate systems, and alkali-halides tor ionic solids. We review the current understanding of PSD and ESD for these systems, including a variety of very recent results. Finally, we discuss an example of the application of ESD to provide precise control of surface chemistry in the synthesis of electronic materials. © 1987.