A new direct structure determination technique, Coherent Bragg Rod Analysis (COBRA), has been developed@footnote 1@ that reveals the atomic structure of epitaxial thin films and interfaces with sub-Angstrom resolution. The measurements take advantage of the high brilliance of x-ray synchrotron radiation from undulator beam lines at the Advanced Photon Source, Argonne National Laboratory. In this presentation we will describe the capability of COBRA to reveal subtle details of the interface structure that cannot be accessed by existing structural methods. The method will be illustrated by several examples drawn from our recent work on epitaxial oxide films, including perovskite ferroelectric heterostructures. This work is carried out in collaboration with Y. Yacoby (Hebrew University, Jerusalem), R. Pindak (NSLS), and E. Stern (University of Washington) and is funded by the U.S. Department of Energy, Basic Energy Sciences, and by FOCUS, a National Science Foundation Frontiers of Physics Center. @FootnoteText@ @footnote 1@ 1. Direct determination of epitaxial interface structure: Gd2O3 passivation of GaAs, Y. Yacoby, E.Stern, J. Cross, D. Brewe, R. Pindak, D. Walko, E. Dufresne and R. Clarke, Nature Materials 1, 99-101 (2002).