1. Mathematical treatment of experimental data on establishing relationships between σs and ɛ with the use of the “Nairi” computer confirmed the usefulness of the equation σs = mɛn for describing experimental hardening curves and indicates the very close relationship between σs and; the correlation coefficient is 0.935–0.993, However, for many of the investigated materials the exponential hardening rule has a somewhat approximate character, which is the result of a change in n with an increase in ɛ. This rule is best fulfilled with the use of the coefficient m and the strain-hardening exponent n determined with ɛ ≥ 1.0. 2. For many metals and alloys the value of n is not a constant but changes with an increase in the degree of strain. For alloys the deformation of which is not complicated by structure and phase transformations the value of n decreases with an increase in ɛ basically up to ɛ ≈ 0.6–0.8 or remains unchanged. Of the investigated materials the value of n is constant over the whole range of considered values of ɛ for technical grade iron and 40Kh and 45Kh steels while for 35 and 18KhGT steels there is an insignificant decrease in n with an increase in ɛ. For alloys having structure and phase transformations during plastic deformation the value of n first increases with an increase in ɛ and then starts to drop.