Interfacial phenomena control the performance of devices employing various oxides and designed to realize phenomena such as spin injection and magnetic coupling. Here we review our work on spin injection into oxide superconductors and briefly mention work on magnetic heterostructures. The focus will be on geometries prepared using ozone-assisted, oxide-molecular beam epitaxy. The implications for our results of recent applications of probes of buried interfaces will be discussed. (c) 2005 Elsevier B.V. All rights reserved.