Many of the science and engineering problems under investiga­ tion at industry, government and university laboratories come under the headings "energy, materials and resources." X-ray analysis plays a key role in these investigations. This is reflected in the content of the present volume of Advances in X-ray Analysis. Nearly half of the papers come under such headings as energy production and conversion, materials optimization and mineral characterization. The remainder continue the long tradition of this series in pre­ senting the latest advances in apparatus and procedures for x-ray diffraction and fluorescence analyses. In keeping with recent practice, this year's Denver Conference on Applications of X-ray Analysis emphasized x-ray diffraction and was co-sponsored by JCPDS, International Center for Diffraction Data. The first group of papers in this volume were presented in a plenary session on unusual specimen preparation, handling and analy­ ses by x-ray diffraction. In the lead paper, D. K. Smith and C. S. Barrett combine their seven decades of experience with surveys of diffractionists throughout the world to present a comprehensive re­ view of non-routine specimen preparation in powder diffractometry. Next, M. J. Camp discusses the particular procedures and constraints under which foresnic laboratories employ diffraction methods. F. A. Mauer and C. R. Robbins discuss a method for characteri­ zation of high temperature-pressure reactions in situ by energy dis­ persive x-ray diffraction that offers the promise of sorting out the mechanisms underlying materials compatibility and durability.