Electromigration or electron-induced-migration (EIM) of oxygen in the hightemperature superconductor YBa2Cu3O7-δ alters the superconducting properties through variations in the oxygen concentration. We study this process with unprecedented spatial resolution and find that the transport of oxygen through a grain boundary into a neighboring grain is unlikely, and that hot electron effects dominate the mechanism for EIM in this system. The extent of the EIM effects implies that grain boundary scattering is strong for these electrons. EIM is induced with the tunnel current from the metal cladding on a near-field optical microscope (NSOM). Variations in the oxygen concentration due to fabrication, aging, and electromigration are imaged optically and corroborated to the grain structure. © 2000 American Institute of Physics.