This book is based on the lecture notes of courses given by the author over the last decade at the Otto-von-Guericke University of Magdeburg and the Technical University of Berlin. Since the author is concerned with researching material t- ory and, in particular, elasto-plasticity, these courses were intended to bring the students close to the frontiers of today knowledge in this particular field, an opportunity now offered also to the reader. The reader should be familiar with vectors and matrices, and with the basics of calculus and analysis. Concerning mechanics, the book starts right from the - ginning without assuming much knowledge of the subject. Hence, the text should be generally comprehensible to all engineers, physicists, mathematicians, and others. At the beginning of each new section, a brief Comment on the Literature c- tains recommendations for further reading. Throughout the text we quote only the important contributions to the subject matter. We are far from being complete or exhaustive in our references, and we apologise to any colleagues not mentioned in spite of their important contributions to the particular items. It is intended to indicate any corrections to this text on our website http://www.uni-magdeburg.de/ifme/l-festigkeit/elastoplasti.html along with remarks from the readers, who are encouraged to send their frank cri- cisms, comments and suggestions to [email protected]. All the author royalties from this issue will be donated to charitable organi- tions like Terres des Hommes.