This text is an introduction to crystal mechanics and includes theories of polycrystalline and continuum plasticity for textured materials. It presents a simple and concise review of the mechanics of crystals and polycrystals and gives methods for solving problems related to the plastic deformation of metals. Along with the basic concepts, essential for the student or nonspecialist, much of the author's pioneering work is emphasized and is presented for the first time in book form. Focussing on plasticity, the text includes a chapter on elasticity, which introduces the reader to transformations of stress and strain from one set of axes to another. The effects of anisotropic thermal expansion on polycrystals are also discussed. The concepts of crystal plasticity are extended to predict the behavior of textured polycrystals and the predicted behavior is related to continuum theories of yielding. The author demonstrates that to solve engineering problems, it is possible to bypass continuum mechanics completely, and use crystallographic analyses directly. With our rapidly growing computer power, such an approach to engineering problems may eventually become routine. Sample problems have been included in the first few chapters and Appendix I to illustrate points and show approaches to solving problems. For novices, helpful appendices have been included to cover fundamentals of geometry, crystallography, and mechanics. Students of materials science, mechanics, crystallography, and engineering may use this textbook for part of a general course on the mechanical behavior of metals.