Concise, logical, and mathematically rigorous, this introduction to the theory of dislocations is addressed primarily to students and researchers in the general areas of mechanics and applied mathematics. Its scope encompasses those aspects of dislocation theory which are closely related to the theories of elasticity and macroscopic plasticity, to modern continuum mechanics, and to the theory of cracks and fracture. The volume incorporates several new and original pieces of work, including a development of the theory of dislocation motion and plastic strain for non-linear materials, a new discussion of the line tension model, revised calculations of the Peierls resistance, and a new development of the van der Merwe theory of crystal interfaces.