The characterization of defect configurations in various perovskite-like substrate materials for high Tc superconductor epitaxial films has been conducted using white beam synchrotron X-ray topography. The substrates were found to contain crystal lattice defects such as twins, dislocations and grain boundaries. It is shown that characterization of substrates can potentially afford insight into factors controlling the properties of the high Tc superconductor tilms supported on them. This can help in the selection of optimum substrate material. Defect formation mechanisms in individual materials as well as their respective influences on the films are discussed. Comparisons between the physical and chemical properties of several potential substrate materials are presented.