This textbook gives a clear, well-illustrated account of the current understanding of the physics of plasticity. The plastic deformation of various types of crystals over a wide range of temperature is treated in terms of dynamical properties of dislocations. Special effects of plasticity, e.g. softening of metals at the superconducting transition and photoplastic effects in semiconducting crystals, are emphasized, as well as creep deformation in metals and composite materials.