This Research Planning Grant will support an investigation of the relation between crystal structure, anisotropy, interplanar spacing, and transition temperature and the physical properties of flux pinning, flux creep, the irreversibility line, and the critical current density. Single crystal samples of the high temperature superconducting single Cu-O layer compounds of the lanthanum, thallium, and mercury cuprates will be grown, characterized and measured. The results of this planning grant will provide a foundation for further study of these strongly layered materials. %%% This Research Planning Grant will support an investigation of the relation between crystal structure and physical properties of the high temperature superconductors (HTS). A limitation in the use of HTS is the control of properties that enhance the current that can flow without resistance in these materials. This investigation will grow single crystals of several classes of HTS having a single copper-oxygen layer and measure the critical current and other parameters and their relation to the crystal structure and the anisotropic properties of these crystals. ***