This book is a comprehensive treatment of the fundamentals of dislocations. Sufficient detail is provided to make the book useful as a underrate text, and extends the treatment of specific problems to stimulate the advanced graduate student. The book covers the elastic theory of straight and curved dislocations, including a chapter on elastic anisotropy. Applications to the theory of dislocation motion at low and high temperatures are presented. Finally, groups of dislocations, grain boundaries, pileups, barriers, and twins are considered.