Severe stress conditions of modern structures and strict weight limitations call for continuous refining of the methods of strength and analysis and optimization of the technologies. This is the first handbook containing extensive information on the influence of the stress on the material properties. Strength and plasticity of materials of various classes under three-dimensional (triaxial) stress, and three-dimensional compression in particular is discussed which makes it possible to specify and choose with a higher degree of justification the models of deformation and the criteria of strength of quasti-brittle materials used in practical calculations. The lifetime of structural materials under conditions of high-cycle loading and complex stress is considered. The influence of the stress mode on the crack growth resistance has been covered in detail. All the numerical data are given in the metric system.