This classic text of elementary dislocation theory has been reprinted to fulfil persistent demand. Because it approaches elementary dislocation theory from its most basic level, the material contained in the volume is as up-to-date as when first published. The text addresses many aspects of dislocation theory, including the nature of dislocations, Burgers vectors, motion and its impact on dislocations, internal stresses of dislocations, and multiplication of dislocations. The topics of this text are fundamental to the theory of dislocation behaviour. Because dislocation is now widely recognized as a key factor determining the behaviour of crystalline solids, specialists in electronics materials, as well as fracture mechanics, and materials science and engineering should have a solid grounding in this field. A large number of problems is provided in the text.