The tensile curves of samples of structural steels and armco-iron in various structural-phase states have been examined. It is shown that the concentrated stage of stretching of metallic materials consists of three periods, the parameters of which (stress σi and degree of deformation δсiн corresponding to the beginning of the period, length δi, rate of stress drop (Δσ / Δδ)i) regularly change with the loss of material plasticity. The periods of the concentrated stage of tension are compared with the fracture zones of the samples and the type of crack.