This book is a comprehensive treatment of the fundamentals of dislocations. Sufficient detail is provided to make the book useful as an undergraduate 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.